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INFECTION,    IMMUNITY 

AND 

SERUM    THERAPY 


'  -^ 


In  RELATION  to  the  INFECTIOUS  DIS- 
EASES which  ATTACK  MAN  ;  WITH 
CONSIDERATIONS  of  THE  ALLIED 
SUBJECTS  OF  AGGLUTINATION, 
PRECIPITATION,  HEMOLYSIS,    ETC. 


H.   T.    RICKETTS,   M.D. 

InUruBor  in  Pathology,   Uni-versity  of  Chicago 


CHICAGO 

AMERICAN    MEDICAL  ASSOCIATION    PRESS 

103    DEARBORN   AVENUE 

1906 


CuriltlGHT.    lOU.j. 
Bi" 

Ami;i;[ca.v  MEuiCAr.  Associatu>.\. 


PREFACE, 

Immimity,  in  its  present  state  of  development, 
with  its  manifold  new  terms  and  special  methods 
of  experimentation,  is  a  subject  which  appears  dif- 
ficult to  one  who  has  not  studied  the  newer  litera- 
ture assiduously  and  grown  into  a  knowledge  of  the 
.  conditions  through  actual  work  in  the  laboratory. 
Much  of  the  literature  is  technical  in  character  and 
appears  in  journals  not  commonly  found  in  the 
hands  of  the  physician  and  student.  Much  of  it 
also  is  comparatively  recent,  and  its  "essence"  has 
not  yet  appeared  in  books  which  are  in  general  use. 
The  literature  of  immunitj^,  moreover,  grows  so 
amazingly  that  the  analysis  even  of  current  works 
is  a -task  of  no  mean  proportions. 

At  the  same  time,  the  subject  is  one  of  great 
interest  and  importance,  and  there  exists  a  gen- 
eral wish,  frequently  expressed,  to  know  more 
about  the  recent  advances  and  the  conditions  which 

-A  have  operated  against  the  success  of  serum  therapy 

■^  on  a  broader  scale. 

?5  The  editor  of  The  Journal  of  the  American  Med- 

^  .  .     . 

■f;  ical    Association^    appreciating    the    need    which 

seemed  to  exist,  requested  the  writer  to  prepare  a 

If"*:,  series  of  articles  on  the  subject  of  "Immunitv," 


405754 


IV  PREFACE. 

wliirh  should  present  the  genei'iil  pi'ineijiles  and 
the  important  theories  and  facts,  in  as  simple  a 
manner  as  possible.  These  articles  appeared  from 
Aveek  to  Aveek  dnring  the  year  of  1905  in  the  jour- 
nal mentioned,  and  after  revision,  and  Avith  such 
additions  as  Avould  contribute  to  the  completeness 
of  the  Avork,  tliey  are  noAV  collected,  in  larger  type, 
in  the  present  A^ohime  and  rmder  a  more  suitable 
title. 

It  Avas  thought  best  to  treat  the  subject  broadly, 
to  begin  Avith  the  fundamental  principles  of  in- 
fection and  resistance  and  to  introduce  the  reader 
to  the  more  complex  conceptions  of  the  present 
time  by  taking  him  briefly  over  the  main  historical 
and  developmental  steps. 

It  Avill  be  oljvious  that  the  vicAVS  of  Ehrlich, 
concerning  the  production  of  antibodies,  the  nature 
of  the  reactions  into  Avhich  the  latter  enter,  and  the 
methods  by  Avhich  bacteria  produce  disease,  haA^e 
l)een  utilized  extensively.  This  course  demands 
no  justification,  Avhen  it  is  appreciated  that  by 
no  other  means  can  one  at  the  present  "time  corre- 
late a  multitude  of  vi'ell-established  facts  Avliich 
bear  on  the  problems  of  immunity.  Whatever  may 
be  the  eventual  fate  of  the  side-chain  theory — and 
certain  phases  of  it  carry  the  aspect  of  finality — Ave 
should  appreciate  as  much  as  possible  the  extent  to 
AA'hich  it  has  shaped  modern  thought,  and  recognize 


PREFACE.  V 

that  it  has  won  an  imperis]ia])lc  })lar-c  in  tlio  his- 
tory of  biologic  progress. 

It  should  also  be  understood  that  the  utilization 
of  the  side-chain  theory  in  no  sense  carries  with  it 
a  negation  of  the  importance  of  phagocytosis,  a 
fact  which  is  plainly  set  forth  on  pages  312-215. 
Without  doubt  the  role  of  the  phagocytes  in  recov- 
ery from  a  large  group  of  infections  is  on  a  better 
and  truer  basis  than  it  has  ever  been  before,  and 
for  this  condition  the  recent  work  on  opsonins  has 
been  most  significant. 

In  relation  to  the  grouping  of  the  infectious 
diseases  adopted  in  Part  Two,  attention  is  called 
to  the  explanatory  paragraph  on  page  235. 

It  will  be  noted  that  a  complete  bibliography  of 
the  subject  of  immunity  has  not  been  added,  and 
this  needs  no  explanation  to  one  who  is  conscious 
of  the  massive  proportions  of  the  literature.  A 
critical  analysis  of  the  entire  literature,  which 
would  not  have  been  in  harmony  with  the  endeavor 
to  present  the  topics  briefly  and  clearly,  and  which 
would  have  made  detailed  references  essential,  has 
not  been  attempted.  The  works  cited  in  the  bibli- 
ography are  largely  analytic  in  character  and  carry 
with  them  more  or  less  complete  references, 
through  which  those  who  are  so  interested  may 
reach  the  original  sources  easily.  This  is  true  par- 
ticularly of  the  handbook  of  Kolle  and  ^Yasser- 


VI  ]' in:  FACE. 

inann  and  of  the  volume  by  ^letelinikoll'.  Almost 
tlie  entire  fourth  volume  of  the  former  is  devoted 
to  the  subject  of  immunity,  the  enormous  litera- 
ture of  -which  is  analyzed  by  different  persons  of 
international  repute.  The  most  recent  literature 
on  the  various  subjects  is  accessible  through  the 
Index  Medicus,  or  the  index  prepared  semi-an- 
nually by  The  Journal  of  the  American  J\Iedical 
Association. 

Tlie  index  at  the  close  of  this  volume  serves  as 
a  glossary  of  terms,  the  explanations  of  which  may 
he  found  on  the  pages  referred  to. 

H.  T.  ElCKETTS. 

Chicago,  February,  190G. 


CONTENTS, 
PART  ONE— GENERAL, 

Chapter  I. 
Parasitism,    Infectiousness,    Contagiousness 1-     (> 

Chapter  II. 
Infectious   Etiology 7-  10 

Chapter  III. 
General   Considerations 17-2.3 

Chapter  IV. 
History  and  Development 24-  34 

Chapter  V. 

Natural  Immunity : 

A.  Protection  Afforded  by  the  Body  Surfaces  35-  41 

B.  The  Protective  Nature  of  Inflammation .  .   41-  46 

C.  The   Antibacterial   and   Antitoxic   Nature 

of   Natural   Immunity 46-  55 

Chapter  VI. 
Acquired    Immunity 56-  64 

Chapter  VII. 

Toxins  and  Antitoxins 65-  77 

Chapter  VIII. 

The   "Structure"'   of  Toxins   and   Antitoxins   and 

the  Nature  of  the  Toxin-Antitoxin  Reaction.  .  .    78-  91 

Chapter  IX. 
Tlie   Plienomena   of  Agglutination 92-104 

Chapter  X. 
The    Nature    of    the    Substances    Concerned    in 
Agglutination    105-118 


Till  COXTlJyTS. 

Chapter  XI. 

Precipitins    119-129 

Chapter  XII. 

A.  General  Properties  of  Bacterieidal  Serum«.  ..  130-141 

B.  Amboceptors   and   Complements 141-lGl 

Chapter  XIII. 
Cytotoxins    102-175 

Chapter  XIV. 
Phagocytosis    17G-194 

Chapter  XV. 
The  Side-Chain  Theory  of  Ehrlich  and  Its  Rela- 
tion to  the  Theory  of  Phagocytosis 195-217 

Chapter  XVI. 
Principles  of  Serum  Therapy 218-234 

PART  TWO-SPECIAL, 

Group  I. — Acquired  Immunity  Is  Chiefly  Antitoxic. 

A. — Bacterial  Diseases: 

Diphtheria    235-244 

Tetanus    244-25G 

Botulism     256-259 

Bacillus   Pyocyaneus 259-262 

Otner   Soluble    Bacterial    Toxins 262 

B. — Intoxication  hy  Soluble  Plant  Toxins: 

Hay    Fever 262-264 

Other  Plant  Toxins 264 

C. — Intoxication  by  Soluble  Animal  Toxins: 

Poisoning  by  Snake  Bites 264-268 

Other    Zootoxins 268 

Group  II. — Acquired  Immunity  Is  Chiefly  Anti- 
bacterial. 

Typhoid    Fever 269-284 

Paratyphoid    Fever 284-288 

Acute   Epidemic   Dysentery 288-294 


CONTENTS.  IX 

Meat  Poisoning  by  Bacillus  Entoritirlis 204-208 

Bacillus    Coli    Cominunis 298-304 

Cholera    304-315 

Plague 315-327 

Anthrax    327-333 

Malta    Fever 333-335 

Group   III. — Acute  Infections   in  Which   Lasting 
Immunity  Is  Not  Established. 

Pneumococcus    Infections — Pneumonia 33G-349 

Streptococci 349-370 

Staphylococci     370-383 

Micrococcus    Catarrhalis 383-384 

Gonorrhea  and  Other  Infections  with  the  Gono- 

coccus    384-388 

Epidemic    Cerebrospinal    Meningitis 388-393 

Influenza    393-399 

Soft    Chancre 399-401 

Bacillus   of   Friedlander    and   Other    Members    of 

the   Capsule-Forming   Group 401-402 

Relapsing    Fever 403-406 

Group   IV. — Chronic   Infections   in   Which   Lasting 
Immunity  Is  Not  Established. 

Tuberculosis     407-445 

Leprosy    445-452 

Glanders     452-458 

Rhinoscleroma     458 

Actinomycosis    458-462 

Madura    Foot 462 

Infections  by  Streptothrix,  Cladothrix  and  Lepto- 

thrix    463 

Oidiomycosis     463-467 

Group  V. — Diseases  of  Protozoon  Etiology. 

Malaria     468-483 

Trypanosomiasis    483-497 

"Spotted  Fever"  of  the  Rocky  Mountain  Stales.  .497-498 
Texas  Fever  as  an  Example  of  Pyroplasmosi-.  .  .499-500 
Amebic   i)ysentery 500-504 


N  VOXTIJNTS. 

SiUL'ospoiiilia    504 

Jiahintidium  Coli   505 

Corc-onionas  Intcstinalis 500 

Trichomonas     507 

Coccidiosis    508 

Group  VI. — J^iskasks  oi-  DouBTirL  on  Unknown 

lvriOLO(iY. 

Hydrophobia    510-521 

Syphilis    522-520 

Yellow    Fever 529-538 

Typhus    Fever 538 

Dengue  Fever 539-541 

Acute   Articular    Klieuniatism 541 

Smallpox   and    Vaccinia 541-555 

Chickenpox    (Varicella)   555 

Scarlet  Fever    550-55!) 

Measles    559-562 

(ierman  Measles    (  Kiitheln) 502 

Whooping  Cough 502-50(1 

Mumps    5(10 

Appendix 507-571 

Bibliography     572 

Index    573-599 

Corrections    600 


PART  ONE—GENERAL. 


CHAPTER  I. 


PARASITISM,,    INFECTIOUSNESS,    CONTAGIOUSNESS. 

Parasitism  is  the  condition  in  which  a  plant,  or  Parasitism. 
an  animal  being,  lives  on  or  within  another  living 
organism.     A  true  parasite  always  derives  its  sus- 
tenance from  the  tissues  of  its  host. 

Some  parasites  may  live  on  a  host  without 
causing  appreciable  damage,  that  is,  they  are  non- 
pathogenic parasites.  In  this  case  they  may  de- 
rive their  nutrition  from  some  of  the  excreted  non- 
living products  of  the  host,  living  as  pure  sapro- 
]:)hytes,^  or  the  amount  of  nutritious  substance 
which  they  'obtain  from  the  host  may  be  so  little 
that  the  health  of  the  latter  is  not  impaired. 

There  is  another  large  class  of  parasites,  how- 
ever, which  under  proper  conditions  cause  severe 
diseases  in  the  host.  Many  pathogenic  microbes  live 
in  and  on  the  skin  without  doing  harm,  but  if  cer- 
tain ones  reach  the  deeper  tissues,  they  may  insti- 
tute pathologic  processes  (e.  g.,  staphylococci).  Any 
organism  Avhich  is  able  to  cause  pathologic  tissue 
changes  or  to  set  up  abnormal  s3miptoms  is  classed 
as  a  patliogenic  parasite.  The  abnormal  processes 
which  they  set  up  are  our  infectious  diseases. 

1.  A  .saprophyte  is  defined  as  a  vegetable  organism 
which  lives  on  dead  organic  matter.  An  organism  which  is 
liabitually  saprophytic  may  become  pathogenic  under  the 
proper  conditions  (bacillus  of  malignant  edema).  And.  on 
the  other  hand,  a  patliogenic  parasite  lives  a  saprophytic 
life,  when  it  grows  in  our  artificial  culture  media. 


IXFECTIOy    AMJ    1.UMLMTY. 


Infectious 
Disease. 


Infestation 
and  Infec- 
tion. 


Contagiousness 
and  Infectious- 
ness. 


Au  inl'eelious  di^ea^;e  is  oue  whic-li  is  caused  by 
living  organisms  which  in  some  way  have  been 
introduced  into  the  tissues  of  the  body.  Accord- 
ingly the  word  lias  reference  to  the  nature  of  the 
cause  of  the  disease.  It  is  from  the  Latin  inficire, 
meaning  to  place  in  or  into. 

Where  living  organisms  exist  on  a  body  sur- 
face, as  the  skin  or  intestinal  tract,  the  surface  is 
.>^aid  to  l)e  infested;  the  skin,  for  example,  is  in- 
fested with  pediculi.  One  may  also  say  that  the 
intestinal  tract  is  infested  with  tape  worms,  but 
here  the  distinction  between  infestation  and  in- 
fection is  not  to  be  draAATi  so  sharply ;  surely  when 
the  larvfe  penetrate  the  intestinal  wall  and  reach 
the  circulation  or  distant  organs  we  must  speak 
of  infection.  But  even  the  adult  tenia  as  it  ex- 
ists in  the  intestines  may  cause  erosions  of  the 
mucous  membrane  or  may  perhaps  burrow  a  slight 
distance  into  the  wall,  a  condition  which  approx- 
imates the  action  of  the  larvfe  in  passing  through 
the  wall;  accordingly  at  some  point  the  distinc- 
tion between  infestation  and  infection  becomes  an 
arbitrary  one. 

Confusion  sometimes  arises  in  using  the  words 
infectious  and  contagious.  A  contagious  disease 
is  one  which  may  be  transmitted  from  one  indi- 
vidual to  another  by  direct  or  indirect  contact; 
the  word  has  reference  to  the  manner  of  transmis- 
si(m  of  an  infection.  Non-infectious  diseases  are 
never  contagious.  Contagiousness  is  well  illus- 
trated in  those  disease  in  which  the  transmi:=6ion 
takes  place  through  the  air.  as  seems  to  be  the 
case  in  smallpox  and  scarlet  fever.  Here  there 
may  be  a  contagious  zone  of  atmosphere  surround- 
ing the  patient,  in  which  the  Airii^;  i.^  ]")roscnt.  and 


Contact 
Infection. 


CONTACT   INFECTION.  3 

by  which  tlie  agent  reaches  the  lungs  oC  one  within 
the  zone.  Contagiousness  is  even  more  striking 
when  it  takes  place  through  the  medium  of  some 
inanimate  substance,  such  as  clothing  or  toys, 
which  were  previously  within  the  contagious  zone 
or  in  direct  contact  with  the  patient.  Such  sub- 
stances, fomites,  were  formerly  thought  to  he  of 
great  importance  in  the  extension  of  yellow  fever; 
a  theory  which  has  been  entirely  exploded  by  the 
proof  that  the  disease  is  transmitted  through  the 
bite>  of  infected  mosquitoes. 

Typhoid  fever  is  not  highly  contagious.  There 
probably  is  no  infected  zone  of  atmosphere  about 
the  patient  in  the  sense  that  there  is  about  a  scar- 
let fever  patient.  Yet  it  frequently  happens  that 
the  nurse  contracts  the  disease  while  caring  for 
her  patient.  It  is  likely  that  she  has  in  some  way 
transferred  the  bacteria  from  the  patient's  sputum, 
urine,  feces  or  fekin  to  her  lips  or  hands  so  that 
eventually  they  found  their  way  into  the  intes- 
tines. At  the  same  time  it  is  not  improbable  that 
the  point  of  entrance  for  the  germs,  i.  e.,  the  in- 
fection atrium,  may  at  times  be  the  lungs,  the  Jil'Jr^*" 
bacteria  having  been  inhaled.  However,  t}T)hoid 
fever  is  usually  a  'Svater  borne"  disease,  seldom 
"air  borne.'' 

We  are  to  look  on  malaria  as  a  strictly  non-con- 
tagious disease,  although  no  doubt  is  possible  as 
to  its  infectiousness.  Ko  amount  of  personal  con- 
tact with  the  patient  will  transmit  it  to  another. 
To  accomplish  transmission  the  parasite  must  be 
actually  injected  into  an  individual,  an  event 
which  happens  exclusively,  it  is  believed,  through 
the  bite  of  a  mosquito  which  has  previously  fed  on 
the  blood  of  a  malarial  patient. 


IM'ECTIOX    AXD    IMMCMTY 


Pathogenesis. 


Mechanical 

and  Toxic 

Injuries. 


Tetanus  is  anothci-  iiuled  example  of  an  iufee- 
tioiis  disease  which  is  not  acquired  by  contact  with 
one  sufl'ering  from  it. 

The  various  parasites  have  ditl'erent  ways  of  in- 
juring the  body.  Tlie  itcli  mite  burrows  into  and 
honeatli  the  oiiidermis,  causin^ii'  nieelianical  ii-rita- 
lioii  ;w  well  as  tlio  inilammatory  reaction  pnxhieed 
by  its  toxic  excretions.  Tlie  loss  of  blood  caused 
by  some  intestinal  ])arasites,  and  the  hemorrlu:ige 
which  follows  from  the  Avounds,  often  lead  to 
grave  anemias  and  the  general  changes  wliich  are 
caused  by  such  anemias.  This  is  especially  the  case 
in  the  duodenal  infection  Avitb  uncinaria  dunden- 
alis   (uncinariasis). 

A  certain  variety  of  Fihirin  smigainis  Jioininis 
produces  disorders  l)y  mechanical ly  blocking  the 
lymph  channels. 

The  Plasmodium  of  malaria  causes  anemia  by 
the  destruction  of  blood  cells. 

The  febril  disturbances  of  infectious  diseases 
are  certainly  due  to  toxic  influences. 

Tt  is  generally  said  that  bacteria  produce  dis- 
turbance* in  both  a  mechanical  and  a  toxic  way. 
However,  the  more  we  learn  about  bacterial  infec- 
tions the  more  important  do  the  toxic  pheno- 
mena become.  It  is  doubtful  if  any  pathogenic 
bacterium  is  entirely  devoid  of  toxic  powers. 

It  is  probable  that  the  bacterial  eml)oli  which 
are  sometimes  found  in  capillaries  and  small  ar- 
teries cause  disturbances  through  the  shutting  off 
of  so  much  circulation,  but  still  greater  damage 
may  result  from  the  action  of  toxins  which  are 
formed  by  the  microbes  making  up  the  emboli. 

In  lobar  pneumonia  we  have  a  good  example  of 
a    mechanical    disturbance    of    importance.      The 


KFFECTii  OF  TOXfjXH.  r, 

alveoli  become  filled  with  a  fibrinous  and  purulent 
exudate  which  makes  a  large  area  of  pulmonary 
tissue  unavailable  for  respiration.  Yet,  even  here, 
the  mechanical  disturl:)ance  lias  arisen  only  as  a 
result  of  the  previous  toxic  action  of  the  pneumo- 
cocci  on  the  capillary  walls  and  the  alveolar  epithe- 
lium, permitting  the  escape  of  the  Idood  and  serum. 

The  toxins  of  bacteria  often  show  a  remarkable  Effects  of 
selective  action  on  one  organ  or  another.  Some 
destroy  the  red  blood  cells  to  a  great  degree 
(staphylococcus  and  streptococcus)  ;  other  toxins 
have  a  special  affinity  for  the  nervous  tissue  (tet- 
anus) ;  some  attack  particularly  the  endothelium 
of  the  vessels^  causing  many  minute  hemorrhages. 
Frequently  bacterial  toxins  cause  areas  of  necrosis 
in  the  lymphoid  and  parenchymatous  organs,  and 
the  granular  degenerations  of  the  latter,  in  acute 
infectious  diseases,  are  Avell  known.  The  albumin 
and  casts  which  appear  in  the  urine  in  many  acute 
febrile  diseases  are  the  result  of  toxic  action  on 
the  epithelium  and  endothelium  of  the  kidneys. 
It  is  said  that  in  anthrax  all  the  glycogen  may 
disappear  from  tlie  liver;  toxins  may  disturb  the 
functions    of    various    organs    to    similar    degree. 

Some  chronic  infections  are  characterized  by  the 
■  development  of  new  connective  tissue  and  vessels ; 
this  is  seen  especially  in  tuberculosis,  syphilis  and 
actinomycosis.  The  import  of  the  new  connective 
tissue  depends  on  its  location.  A  large  amount  of 
it  may  form  in  pre-existing  connective  tissues  with 
no  consequent  harm ;  but  even  a  small  scar,  gTimma 
or  tubercle  in  the  brain  may  cause  serious  results. 

It  has  been  stated  above  that  infectious  diseases  infectious 
are  caused  by  living  pathogenic  organisms.     In-  ^"''**"""*- 
vestigations  have  shown,  however,  that  the  toxic 


G  lyFECTlOX    A.\L)    IMMLMTY. 

proiliicts  of  .some  organisms  can  be  prepared  and 
separated  from  the  organisms  themselves  by  filtra- 
tion, and  that  such  microbe-free  toxins  when  in- 
jected into  animals  may  cause  the  same  symptoms 
that  are  produced  by  the  bacteria  themselves  (teta- 
nus and  diphtheria).  Accordingly,  for  the  sake  of 
convenience,  these  toxins  also  may  be  considered 
among  the  infectious  agents,  even  though  sepa- 
rated from  their  corresponding  bacteria.  The  va- 
rious infectious  agents,  including  these  toxins,  find 
their  proper  places  in  the  following  classification, 
which,  for  the  most  part,  is  that  of  von  Behring: 
I.  Living  (i.  c.,  pathogenic  parasites). 

A.  Macroparasites  (e.  g.,  intestinal  worms, 

pediculi). 

B.  Microparasites. 

1.  Bacteria  (fission  fungi :  each  cell 
divides  into  two  in  proliferating) . 

2.  Fungi  of  more  complex  organiza- 
tion (e.  g.,  aspergillum,  oidia). 

3.  Protozoa  (e.  g.,  plasmodium  mala- 
ria, ameba  coli). 

1\.   Xdii-living  (i.  e.,  toxins). 

A.  Animal  toxins  (e.  g.,  snake  venom). 

B.  Vegetable  toxins. 

1.  Xon-bacterial  (e.  g.,  abrin,  from  the 
jequirity  bean;  ricin,  from  the  cas- 
tor oil  bean;  these  are  strong  red 
corpuscle  poisons,  chiefly  of  experi- 
mental interest). 

2.  Bacterial. 

a.  Soluble  bacterial  toxins  (diph- 
theria and  tetanus). 

b.  Intracellular  bacterial  toxins, 
which  are  not  secreted  by  tlie 
cells  in  a  soluble  form. 


CHAPTER  II. 


Koch's 
Laws. 


INFECTIOUS    ETIOLOGY. 

The  microbic  cause  of  a  disease  must  he  in  hand 
before  a  logical  attempt  can  be  made  to  prepare  a 
specific  immune  serum.  It  is  not  in  all  cases  nec- 
essary that  the  organism  be  cultivated  artificially, 
however ;  the  conditions  in  rinderpest  may  be  cited 
in  which  the  body  fluids  of  a  diseased  animal, 
known  to  contain  the  infectioiis  agent,  are  used 
for  immunization,  although  the  microbe  itself  can 
not.  as  yet  be  cultivated  or  recognized. 

There  are  so  many  possibilities  of  error,  and  so 
many  errors  have  actually  been  made  in  regard  to 
infectious  etiology,  that  certain  requirements  in 
the  way  of  proof  are  now  habitually  demanded  be- 
fore a  particular  organism  can  be  accepted  as  the 
cause  of  a  disease.  These  requirements  are  most 
frequently  expressed  in  the  form  of  Koch's  laws, 
which  may  be  stated  as  follows  1.  The  suspected 
organism  must  be  found  constantly  in  the  proper 
tissues  of  an  animal  suffering  from  the  disease,  or 
which  has  died  from  it.  2.  The  organism  must  be 
cultivated  artificially  in  a  pure  state.  3.  It  must 
be  possible  to  reproduce  the  disease  in  a  suitable 
animal  by  inoculation  with  the  pure  culture.  4. 
The  organism  must  again  be  cultivated  in  a  pure 
state  from  the  tissues  of  the  experiment  animal. 

Since  these  laws  were  formulated  another  proce-  Agglutination 

Test 

dure  has  been  developed  which  may  give  valuable 
evidence  as  to  etiology.  This  pertains  to  the  ag- 
glutination test,  or,  as  we  speak  of  it  in  connection 
with   typhoid   fever,    the    Gruber-Widal    reaction. 


S  IXFKCTIOX    AM>    IMMl'MTY. 

'J'his  principle,  that  in  the  aequinn--  of  iiumiinily 
to  a  niicrobic  infection  the  serum  of  an  individual 
gains  in  agglutinatino-  power  for  the  micro-organ- 
ism, has  been  found  to  hold  trne  in  many  infec- 
tions. Consequently,  if  one  has  in  hand  the  speci- 
fic micro-organism  for  a  disease,  he  would  expect 
the  serum  of  a  patient  sick  of  this  disease  to  have  a 
stronger  agglutinating  power  for  this  micro-or- 
ganism than  for  others  which  were  accidentally 
present;  and  this  power  would  also  be  greater  than 
that  posse>sed  by  the  serum  of  one  who  had  not 
had  this  particular  disease.  In  spite  of  some  pos- 
sibilities of  error  the  a^'glutination  test  lias  been 
of  distinct  value  in  the  recognition  of  the  specific 
micro-organisms  in  certain  diseases,  as  in  the  case 
of  the  germ  of  epidemic  dysentery  (Shiga). 
Obstacles  AH  Koch's  laws  have  not  been  complied  with  in 
Laws,  certain  cases,  because  of  various  difficulties 
which  have  been  encountered.  First,  the  patho- 
genic protozoa  can  not  be  cultivated  on  artificial 
media  (we  must  except  the  success  of  Xovy  and 
]\IcXeal  with  certain  trypanosomas,  and  of  Strong 
with  the  ameba  coli  under  symbiotic  conditions)  ; 
second,  certain  bacteria  which  may  be  found  con- 
stantly in  a  given  disease  have  not  been  cultivated 
artificially  (spirillum  of  recurrent  fever)  ;  third, 
there  are  a  few  diseases  which  are  peculiar  to  man 
and  accordingly  can  not  be  reproduced  in  experi- 
ment animals  (leprosy,  influenza,  scarlet  fever, 
measles,  etc.)  ;  fourth,  some  infectious  agents  are 
pathogenic  for  experiment  animals,  but  do  not 
reproduce  in  them  a  clinical  or  anatomic  condition 
identical  with  that  found  in  the  original  animal 
(typhoid). 
Furthermore,  failure  to  com])ly  with  all  the  re- 


KOCIVH  L.nV'.S'.  9 

quirements  enumerated  does  not,  in  sonic  cases, 
disqualify  tlie  organism  as  the  causal  factor.  If 
an  organism  is  found  constantly  in  characteristic 
sites  in  a  given  disease  and  not  in  other  infections, 
and  if  at  the  same  time  other  microbes  are  not 
present  or  are  present  inconstantly  or  through  ac- 
cident, there  could  be  little  or  no  hesitation  in  ac- 
cepting this  organism  as  the  cause  of  the  disease, 
even  if  it  were  impossible  to  cultivate  it  or  to  trans- 
fer the  disease  to  animals.  The  typhoid  bacillus 
has  been  cultivated  from  characteristic  foci  (stools, 
blood,  spleen,  urine,  rose  spots)  in  such  a  large 
number  of  cases,  and  the  bactericidal  and  agglu- 
tinating powers  of  the  patient's  serum  against  this 
organism  are  so  distinctive,  that  compliance  with 
the  third  law,  though  desirable,  is  not  now  essen- 
tial. The  conditions  are  similar  in  reference  to 
cholera  and  the  cholera  vibrio. 

The  conditions  are  so  imique  in  some  diseases 
that,  although  all  Koch's  laws  have  not  been  met 
literally,  certain  equivalents  have  been  met.  To 
illustrate,  we  may  consider  an  anopheles  mosquito 
which  has  become  infected  with  the  plasmodium 
of  malaria  by  biting  a  malarial  patient,  as  a  cul- 
ture medium:  and  the  transferring  of  the  infection 
to  another  patient  by  the  bite  of  this  mosquito  as 
the  inoculation  experiment  which  is  desired. 

The  term  "specific  infectious  disease"  has  come  specific 
to  have  a  very  special  meaning.  It  is  applied  to  a  Diseases. 
disease  having  characteristic  clinical  and  anatomic 
phenomena,  which  can  be  caused  only  by  one  par- 
ticular micro-organism.  Among  the  diseases 
which  come  within  the  limits  of  this  brief  defini- 
tion, the  following  may  be  enumerated  (the  micro- 
organism which  is  the  cause  of  each  disease  being 
also  given)  : 


10 


IXFECTIOX  Ayn  IMMVyiTY. 


Lnknown 
Etiology. 


Diplitheria 

Tetanus 

Typlioid  fever 

Cliolora 

Anthrax 

Tuberculosis 

Leprosy 

Plao'ue 


Bacillus  dijih ih cricv 
Bacillus  tctani 
Bacillus  iyphosus 
Vibrio  cliolerce 
Bacillus  anthracis 
Bacillns  tuberculosis 
Bacillus  Icprce 
Bacillus  pcstis 


Dysentei-y    (bacillary)  Bacillus  dysenteriai 


Intluenza 
Glanders   (farcy) 
Chancroid 

Recurrent  fever 
(lonorrhea 


Bacillus  influenzae 

Bacillus  mallei 

Bacillus    cliancri    mollis 

(Ducrey) 
8p irillu m  oh crmcieri 
Micrococcus  gonorrhece 
P^pidemic  cerebrospi-    Diplococcus   intracellula- 
ris     mcningiiidis     (of 
Weichselbaum) 
Actinomyces      hovis      et 

ho  minis 
Blastomycetes  and  Oidia 
Plasmodium  malarice 

A  large  number  of  animal  diseases  have  their 
specific  microbe.^,  as  do  certain  other  human  dis- 
eases which  hardly  concern  us  as  to  the  subject  in 
hand. 

In  addition  to  the  diseases  mentioned,  there  are 
several,  of  unknown  etiology,  which  from  analogy 
we  must  recognize  as  specific.  Scarlet  fever, 
measles,  German  measles,  chickenpox,  smallpox, 
yellow  fever,  typhus  fever,  hydrophobia  and  syphi- 
lis, are  undoubtedly  due  to  micro-organisms.  Mal- 
lory  recently   found   in  the  skin  of   four  scarlet 


nal  meningitis 

Actinomycosis 

Blastomycosis 
Malaria 


UNKNOWN  ETIOLOGY.  11 

fever  patients  a  protozoon-like  body  which  he  be- 
lieves to  be  the  cause  of  the  disease,  although  he 
admits  that  much  desired  proof  has  not  been  ob- 
tained. The  Diplococcus  scarlatince  of  Class, 
which  a  few  years  ago  acquired  some  notoriety, 
has  not  been  able  to  stand  as  the  cause  of  scarlet 
fever  in  the  face  of  rigid  investigation. 

Parker,  Beyer  and  Pothier  have  announced  the 
discovery  of  a  protozoon  (?)  Myxococcidium 
stegomyice,  in  the  mosquitoes  which  infect  man 
with  yellow  fever;  but  Carroll  maintains  that  this 
organism  has  no  relation  to  the  production  of  the 
disease.  The  Bacillus  icieroides,  which  Sanarelli 
found  in  a  rather  high  percentage  of  cases,  is  now 
generally  considered  as  a  contaminating  organism. 

It  is  possible  that  smallpox  and  vaccinia  will  be 
eliminated  from  the  diseases  of  unlcnown  causa- 
tion, owing  to  the  evidence  of  protozoon  etiology 
that  Councilman  and  his  colaborers  have  obtained ; 
however,  for  the  present,  the  question  may  be  con- 
sidered sub  judice  in  view  of  the  fact  that  the 
forms  described  bear  a  close  resemblance  to  cer- 
tain well-knoAvn  types  of  cell  degeneration. 

The  following  animal  diseases,  of  unknown 
etiology,  may  also  be  mentioned  in  this  connec- 
tion: Foot  and  mouth  disease,  peripneumonia, 
bovine  pest,  sheep-pox  (clavelee),  chicken-typhus 
or  chicken-pest  and  epithelioma  contagiosum  of 
fowls. 

The  following  appear  to  be  the  chief  reasons  for  obstacles  to 

DiscovGrv  OT 

the  failure  to  discover  the  organisms  of  these  dis-    Microbes. 
eases :     1.  Inability  to  cultivate  the  microbe.     2. 
Mixed,  or  symbiotic  infections.     It  is  conceivable 
that  in  some  case   the  combined  action  of  two 
micro-organisms   may   be  necessary  to   cause   the 


12 


/.\  Fi:cTI()\    .1  A  /'  /  \IML MTY. 


Filterability 
of  Viruses. 


Non-Specific 
Infectious 
Processes. 


disease.  The  non-toxic  pi'oducts  of  the  two  may 
synthesize  to  form  a  toxic  sul)staiice  (Hektoen.)  3. 
Unstained  ability  of  ihv  microbe.  4.  Ultramiscro- 
scapic  size.  The  organism  of  the  peripneumonia  of 
cattle  was  cultivated  by  Nocard  and  Eoux  by  grow- 
ing it  in  a  closed  collodion  sac  which  was  placed  in 
the  ]:)eritoneal  cavity  of  suitable  animals.  It  is  so 
small  that  its  form  can  not  be  made  out.  and 
growth  is  recognized  only  by  clouding  of  the 
culture  medium,  and  the  increased  virulence  of  the 
latter  for  animals. 

Some  valuable  information  has  been  obtained 
l)y  observing  whether  the  infectious  agents  are 
so  small  tliat  they  will  pass  through  dense  filters 
of  porcelain  or  infusorial  earth.  It  has  been  found 
that  the  viruses  of  foot  and  mouth  disease,  peri- 
pneumonia, rinderpest,  sheep-pox,  chicken-typhus, 
horse  sickness,  epithelioma  contagiosum  of  fowls, 
and  yellow  fever  are  filteral)le,  i.  e..  they  pass 
through  the  filter.  This  is  determined  by  inject- 
ing the  filtered  culture  medium  or  serum  into  sus- 
ceptible animals.  The  viruses  of  smallpox  and 
vaccinia  are  said  to  be  non-filterable.  Success  in 
filtering  the  hydrophobia  virus  has  recently  been 
claimed  by  Eemlinger.  Inasmuch  as  scarlet  fever, 
measles,  chicken-pox,  typhus  fever  and  syphilis* 
can  not  be  produced  in  animals,  the  filteraljility  of 
their  viruses  is  not  at  present  susceptible  of  dem- 
onstration. 

There  is  a  marked  tendency  in  many  diseases, 
typhoid,  cholera,  malaria,  etc.,  for  characteristic 
organs  or  groups  of  organs  to  be  involved  in  some 
particular   manner.      These   are    features    which 


*  Uecently     syphilis     lias     been     iuocnlalefl     sMcccssf\illy 
into  antln-opoid  apes.      (Metchnikoff  and  Konx.) 


NON-BUSVErrinf/JTy.  \  ■'. 

stamp  them  as  specific  diseases.  On  the  other 
hand,  a  large  nnniber  of  iiiicro-organisms  cause  no 
Avcll-deflned  clinical  and  anatomic  disease,  l)ut, 
depending  on  various  accidents,  cause  an  intlam- 
ination  now  in  one  organ,  now  in  another. 

Suppuration  is  not  a  specific  disease,  because 
the  pyogenic  power  is  common  to  a  large  number 
of  microbes.  A  diphtheritic  or  pseudo-diphtheri- 
tic process  in  the  mouth  and  throat  may  be  caused 
by  the  diphtheria  hacillus,  streptococcus,  staphylo- 
coccus, oidium  or  yeasts;  bronchitis  may  be  caused 
by  the  influenza,  tubercle,  plague  and  typlioid 
bacilli,  and  by  the  infecting  agents  of  the  acute 
exanthemata,  etc. ;  pulmonitis  by  the  pneumococ- 
cus,  streptococcus,  tubercle,  plague,  Friedlander 
and  influenza  l^acilli,  oidium,  actinomyces,  etc. ; 
meningitis  by  the  tubercle  and  influenza  bacilli, 
streptococcus,  staphylococcus,  pneumococcus,  go  no- 
coccus,  diplococcus  of  epidemic  meningitis,  the 
syphilis  virus,  etc. ;  arthritis  by  the  streptococcus, 
staphylococcus,  tubercle  bacillus,  gonococcus,  the 
virus  of  rheumatic  fever,  etc. ;  endocarditis  by  the 
streptococcus,  staphylococcus,  gonococcus,  pneu- 
mococcus, tubercle  bacillus,  etc.,  and  septicemia 
by  a  whole  host  of  organisms  aside  from  those 
mentioned  as  causing  specific  diseases. 

Within  certain  limits,  however,  there  is  often  a 
degree  of  specifi.city  in  the  processes  produced  by 
some  of  the  organisms  mentioned,  which  some- 
times allows  of  clinical  and  anatomic  differentia- 
tion. The  infiltrating  and  rapidly  extending  in- 
vasion of  the  subcutaneous  and  connective  tissues 
caused  by  the  streptococcus  can  often  be  distin- 
guished clinically  from  the  slower,  more  circum- 
scribed process  of  the  staphylococcus.     The  condi- 


14  INFECriOX  AXD  IMMUNITY. 

tioii.s  induced  by  the  Bacillus  aerogcncs  capsulatus, 
the  bacillus  of  malignant  edema,  are,  in  turn,  dif- 
ferent from  those  of  tlic  streptococcus  and  staphy- 
lococcus. The  pneumococcus  commonly  causes 
the  consolidation  of  rather  extensive  areas  of  tlie 
lung,  whereas  the  streptococcus  and  the  bacillus 
of  Friedlander  are  more  often  found  in  the  lobu- 
lar consolidations.  The  membranous  inflamma- 
tion of  diphtheria  may  in  favorable  cases  be  distin- 
guished from  that  of  the  pyogenic  organisms  with- 
out bacteriologic  aids ;  in  this  possibility,  however, 
there  lies  no  justification  for  neglect  of  tlie  bac- 
teriologic examination. 
Mixed        The  coexistence  of  two  or  more  micro-organisms 

Infections.     .  ,  .  ,  ti  •  •         j?    j?  , 

]n  a  morbid  condition  is  of  frequent  occurrence, 
and  some  of  the  most  interesting  and  important 
phenomena  of  infectious  diseases  are  referable  to 
mixed,  secondary  or  superimposed  infections. 

Two  exogenous  infections  may  attack  an  indi- 
vidual at  the  same  time.  ^leasles  and  scarlet  fever 
and  diphtheria  and  scarlet  fever  have  been  known 
to  coexist.  Pneumococcus  pneumonia  and  typhoid 
fever,  chancre  and  soft  chancre  with  pus  cocci, 
syphilis  and  gonorrhea,  diphtheria  with  strepto- 
cocci, tetanus  with  gangrene-producing  organisms, 
are  common  observations.  One  organism  may  in- 
tensify the  virulence  of  another.  Diphtheria  ac- 
companied by  streptococcus  infection  seems  to  l)e 
more  virulent  than  diphtheria  alone.  It  is  also 
believed  that  the  presence  of  aerol)ie  organisms 
(those  which  demand  oxygen  for  their  develop- 
ment) in  a  wound  infected  with  the  tetanus  bacil- 
lus or  the  bacillus  of  malignant  edema  (anaeroliic 
organisms),  may  increase  the  virulence  of  these 
infections.     Streptococci    are   probably    important 


MIXED  INFECT  ION  f^.  15 

organisms  in  scarlet  fever,  for  they  are  present  in 
nnusual  nnmbers  in  the  throat  lesions  and  are 
often  found  in  fatal  cases  in  all  the  organs,  yet  it 
is  believed  that  they  constitute  only  a  mixed  or 
secondary  infection  superimposed  on  that  of  the 
scarlatina  virus.  The  conditions  are  somewhat 
similar  in  smallpox,  the  pustules  of  which  invari- 
ably contain  streptococci,  staphylococci,  or  both. 
In  both  scarlatina  and  smallpox  these  secondary 
infections  may  be  responsible  for  many  fatalities. 

Pneumococcus  pneumonia  occurring  during  the 
course  of,  or  during  convalescence  from  the  erup- 
tive fevers,  diphtheria,  typhoid  fever  or  erysipelas ; 
a  streptococcus  septicemia  developing  during 
typhoid  (giving  rise  to  an  irregular  temperature 
curve),  streptococcus  infection  of  tubercular  cavi- 
ties, and  the  development  of  acute  tuberculosis 
during  measles — rthese  are  important  examples  of 
secondary  infections. 

We  should  naturally  expect  that  the  presence  of 
a  severe  secondary  infection  might  embarrass  at- 
tempts at  serum  therapy.  Experience  on  this 
point  is  practically  limited  to  diphtheria,  and 
there  is  no  lack  of  evidence  to  show  that  the  dis- 
ease when  complicated  by  severe  streptococcus  in- 
fection often  can  not  be  controlled  by  antitoxin 
treatment. 

It  may  be  emphasized  that  there  are  certain  dis-  infectious 
eases  in  which  a  wide  dissemination  of  the  bac- 
teria is  not  necessary  for  the  production  of  morbid 
phenomena;  where,  in  fact,  they  may  be  entirely 
localized  (diphtheria,  tetanus),  and  the  symptoms 
are  produced  by  virulent  toxins  which  are  readily 
dissolved  in  the  body  fluids  and  carried  to  impor- 
tant organs.     More  especially  are  those  microbes 


10  rXFKCTlOX  AXn  IMMIXITY. 

placed  in  this  class  wliidi  ihmIiut  their  spofitic 
disease-producing  toxins  in  a  soluhlc  foi'ni  when 
grown  in  our  artificial  cnhuiT  media  (houillon). 
The  bacilli  of  diphtheria,  tetanus,  botulism  and 
the  pyocyanous  liaeillus  belong  distinctively  to  this 
group. 

Snake  venom  and  araclinolysin  (spider  poison) 
are  the  best  known  exam])les  of  soluble  animal 
toxins.  As  will  appear  later,  the  serums  of  all 
animals  probably  contain  a  variety  of  toxins  which 
are  injurious  to  one  or  more  species  of  animals. 


CHAPTEE  III. 


GENERAL    CONSIDERATIONS. 


By  imirmnity  we  "understand  that  condition  in  Definition. 
which  an  individual  or  a  species  of  animals  exhib- 
its unusual  or  complete  resistance  to  an  infection 
for  which  other  individuals  or  other  species  show 
a  greater  or  less  degree  of  susceptibility.  Immune 
is  from  the  Latin  immunise  which  originally  ap- 
plied to  one  who  was  exempt  from  a  public  service, 
exempt  from  tribute,  or  free.  Although  the  word 
retained  this  civil  meaning  for  centuries,  and  still 
retains  it  in  certain  connections,  it  also  had,  even 
in  ancient  times,  a  limited  application  to  the  pro- 
tection which  an  individual  might  possess  against 
poisons.  It  is  seen,  for  example,  in  descriptions 
of  a  tribe  inhabiting  Northern  Africa,  the  Psylli, 
who  possessed  a  natural  immunity  to  the  bites  of 
poisonous  snakes.  Although  we  may  be  certain 
from  this  and  other  references  that  a  condition  of 
immunity  was  recognized  in  very  ancient  times, 
the  present  significance  of  the  term  has  developed 
largely  from  a  better  understanding  of  the  nature 
of  infectious  diseases  and  of  the  conditions  upon 
which  the  resistance  of  the  body  depends. 

As  the  definition  suggests,  we  do  not  think  of  Diseases 

...  ^  T-,    .    T  , ,       T.  Concerned  In 

immunity  to  such  processes  as  Bright  s  disease,  immunity. 
arteriosclerosis  or  the  metabolic  diseases,  but  only 
to  those  which  we  have  learned  to  recognize  as  in- 
fectious. 

Immunity  has  no  necessary  relationship  to  the 
degree  of  contagiousness  of  an  infectious  disease. 


18 


INFECTION  AND  IMMUNITY. 


Acquired 
Immunity. 


Natural 
Immunity. 


Family  Suscep- 
tibility and 
Immunity. 


although  some  of  the  most  striking  and  certainlj^ 
the  most  common  examples  of  immunit}^  are  seen 
in  relation  to  such  infections  (as  scarlet  fever  and 
smallpox).  Tetanus,  on  the  other  hand,  which  is 
absolutely  non-contagious,  can  likewise  give  rise 
to  a  high  degree  of  immunity. 

iSTo  medical  fact  is  more  widely"  known  among 
intelligent  people  than  that  an  attack  of  certain 
of  our  infectious  diseases  brings  about  some  kind 
of  change  in  the  patient's  tissues  which  protects 
him,  or  renders  him  immune,  against  further  at- 
tacks of  the  same  disease.  Inasmuch  as  he  was 
previously  susceptible,  the  new  property  is  an  ac- 
quired one,  and  he  is  now  said  to  possess  an  ac- 
quired immunity  against  this  infection. 

It  is  also  well  Iniown  that  many  diseases  which 
attack  man  can  not  be  inoculated  into  animals, 
and  biologists  are.  familiar  with  many  examples 
of  immunit}^  which  are  confined  to  particular  spe- 
cies. The  lower  animals  apparently  can  not  be  in- 
fected with  scarlet  fever  or  measles,  nor  man  vidth 
chicken  cholera.  The  negro  is  less  susceptible 
than  the  white  man  to  3^ellow  fever.  The  resist- 
ance which  these  examples  illustrate  has  occurred 
naturally,  not  through  having  the  disease;  it  is  a 
natural  immunity. 

Natural  immunit}^  is,  for  the  most  part,  an  in- 
lierited  condition;  this  certainly  is  the  case  where 
a  whole  class  of  animals  is  involved.  Similarly, 
the  susceptibility  which  is  peculiar  to  a  species 
must  be  he^editar5^  It  is  often  said  of  some  dis- 
eases that  they  run  in  families ;  e.  g.,  carcinoma, 
gout,  insanity.  This  appears  to  be  just  as  true  of 
some  infectious  diseases,  the  most  noteworthy  ex- 
ample of  which  is  probably  tuberculosis.    In  con- 


NATURAL  IMMUNITY.  19 

trast  to  this  inherited  susceptibility  is  an  inherited 
immunity,  which  may  also  run  in  families.  It  is 
not  so  easy  to  adduce  examples  of  thisi.  We  are  in 
the  habit  of  thinking  of  the  individual  who  can 
resist  all  infections  as  representing  a  standard. 
He,  however,  is  above  the  average  in  resistance, 
and  the  average  is  our  proper  standard  for  esti- 
mating the  resistance  of  a  species  or  race  of  ani- 
mals. It  is  undoubtedly  true  that  some  families 
possess  an  unusual  resistance  to  tuberculosis. 
Furthermore,  experimental  work  with  animals  has 
proved  that,  within  limits,  an  immunity  to  cer- 
tain infections  (e.  g.,  tetanus)  acquired  by  a.  fe- 
male may  be  transmitted  to  her  offspring.  Even 
in  a  given  family,  however,  there  are  often  marked 
variations  in  susceptibility  and  resistance.  One 
child  may  contract  scarlet  fever,  while  his  brother, 
living  under  exactly  the  same  conditions,  may 
escape  it.  There  is,  moreover,  much  reason  to  be- 
lieve that  the  same  individual  varies  greatly  in  his 
resistance  at  different  times  and  under  different 
conditions.  Hence,  the  personal  equation,  as  rep- 
resented by  individual  resistance  or  individual  sus- 
ceptibility, is  of  no  small  consequence. 

The  facts  mentioned  were  familiar  long  before 
anything  was  known  regarding  the  principles  on 
which  they  depend.  Subsequent  to  the  discovery 
of  some  of  these  principles  (to  be  considered 
later),  it  became  convenient  and  necessary  to  rec- 
ognize other  special  types  of  immunity,  although 
any  type  which  can  be  conceived  must  still  find  a 
place  under  either  natural  or  acquired  immunity. 

Although  such  diseases  as  typhoid  and  cholera  Antibacterial 

.     T    1  '  T     ,       •  ,  and  Antitoxic 

are  accompanied  by  pronounced  toxic  symptoms,  immimity. 
the  poisonous  substances  seem  to  be  integrally  as- 


20  INFECTION  AND  IMMUNITY. 

sociated   with  the  bacterial   protoplasm   and  not 
secreted  in  a  soluble  or  diffusible  form  by  the  liv- 
ing cell ;  the}^  are  spoken  of  as  intracellular  toxins 
or  endotoxins.     Observations  point  to  the  belief 
that  the  endotoxins  are  liberated  only  after  the 
bacteria    are    killed    and    dissolved.      When    one, 
through  infection,  has  acquired  immunity  toi  ty- 
phoid or  cholera,  his  fresh  serum  is  able  to  kill  the 
respective  bacterium,  but  apparently  is  not  able  to 
neutralize  its  toxic  substance.    Hence,  on  the  basis 
of  the  nature  of  the  serum,  immunity  to  such  dis- 
eases is   spoken  of   as   antibacterial  rather  than 
antitoxic.  On  the  other  hand,  the  symptoms  which 
are  so  characteristic  of  tetanus  are  produced  not 
by  contact  of  the  bacteria  with  the  nervous  system, 
but  rather  through  the  specific  soluble  toxin  which 
is  secreted  by  the  bacilli  in  the  wound  where  they 
reside.    This  poison,  or  toxin,  is  carried  from  the 
wound  to  the  nervous  system  through  the  lymph- 
atic or  blood  circulation,  the  bacterium  itself  not 
being  transported.    Therefore,  although  tetanus  is 
a  bacterial  disease,  it  is  at  the  same  time  and  in  a 
peculiar  sense  a  toxic  disease. 

The  serum  of  an  animal  which  has  acquired  im- 
munity to  diphtheria  or  tetanus  neutralizes  the  cor- 
responding soluble  toxin,  but  does  not  necessarily 
injure  the  micro-organism  itself.  That  is  to  sa)^, 
the  immunity  is  antitoxic.  Experience  has  shown 
that  this  distinction  between  antibacterial  and  an- 
titoxic immunity  is  an  important  one,  and  the 
differentiation  is  very  sharp  in  some  instances. 
In  many  examples  of  natural  immunity,  the  re- 
sistance can  not  be  attributed  so  specifically  to  anti- 
bacterial or  antitoxic  serum  properties.  This  is  re- 
ferred to  later. 


ACQUIRED  IMMUNITY.  21 

Immunity. 


Immunity  which  results  from  an  infection  de-  ^'^*'^® 


pends  on  a  specific  reaction  on  the  part  of  the 
tissue  cells  in  response  to  the  chemical  injury  pro- 
duced by  the  bacteria  or  their  toxins.  The  indica- 
tion of  the  occurrence  of  such  a  reaction  lies,  first, 
in  the  recovery  of  the  patient,  and,  second,  in  the 
new  antitoxic  or  antibacterial  power  which  may  be 
demonstrated  in  the  serum.  In  view  of  the  active 
part  played  by  the  body  in  establishing  this  new 
resistance,  the  condition  is  referred  to  as  an  active 
immunity.  In  the  preparation  of  various  anti- 
toxic and  antibacterial  serums  for  commercial  pur- 
poses, a  condition  of  active  immunity  is  deliberate- 
ly produced  in  the  animals  (the  horse,  for  ex^ra- 
ple)  by  the  injection  of  the  toxins  or  of  the  bac- 
teria. 

Contrariwise,  the  resistance  which  is  established  Passive 

'  Immunity. 

in  an  individual  through  the  injection  of  an  im- 
mune serum  (such  as  diphtheria  antitoxin)'  is  a 
passive  immunity,  since  it  depends  on  the  intro- 
duction of  ready-made  immunizing  substances 
rather  than  on  their  production  through  an  active 
process  on  the  part  of  the  one  injected.  Active 
and  passive  immunity,  then,  are  varieties  of  ac- 
quired immunit}^  Depending  on  the  disease 
which  caused  the  immunity,  or  on  the  character 
of  the  serum  injected,  they  may  be  either  anti- 
bacterial or  antitoxic. 

Any  one  of  the  types  mentioned  may  be  either  Relative  and 
relative  or  absolute;  synonyms  are  partial  and  immunity. 
complete.  If  absolute,  infection  is  impossible.  If 
only  relative,  different  conditions  may  be  made 
to  prevail  which  would  render  infection  possible; 
for  example,  a  large  number  of  bacteria  will  often 
cause  an  infection  where  a  smaller  number  fails 


-  22  IXFECTIOX  AXD  IMMUXITY. 

to  do  so.  Tlicre  may  also  be  a  temporary  decrease 
in  one's  resistance  through  overwork,  hunger  or  ex- 
posure.   Immunity  is  usually  relative. 

^'**t>f'"*(M  ^y  proper  combinations  of  the  terms  which 
have  been  enumerated,  one  may  describe  somewhat 
accurately  the  different  forms  of  immunity.  Thus, 
a  child  which  has  received  a  prophylactic  injec- 
tion of  diphtheria  antitoxin  is  in  a  state  of  ac- 
quired passive  antitoxic  immunity  to  diphtheria. 
If  immunity  to  t}^hoid  has  developed  as  a  result 
of  the  disease,  the  condition  is  that  of  an  acquired 
active  antibacterial  immunity,  etc.  Accordingly, 
although  the  terms  may  be  somewhat  confusing, 
.it  is  seen  that  they  are  in  no  sense  contradictory. 
The  following  classification  of  immunity  is  con- 
venient, although  in  giving  it,  we  must  recognize 
that  it  probably  does  not  include  all  types  of  im- 
munity. At  this  point  the  single  example  may  be 
cited,  that  the  chicken  is  very  resistant  to  tetanus 
toxin,  although  its  serum  contains  no  antitoxin ; 
hence  in  this  instance  we  could  hardly  speak  of 
antitoxic  immunity  to  tetanus,  but  rather  of  non- 
susceptibility  to  the  toxin. 

f  Natural.  T 

The  inherited  immunity  of  species  and  Anti- 
varieties  of  animals.  I  bacter- 
Inherited  family  or  individual  immunity.  !-  ial  or 
rVcquired.  Anti- 
Active.  I  toxic. 
Passive.  J 

„  L.     ".'■ug       In  many  of  these  conditions  proper  biologic  ex- 

Habituation.  ,  -n     n  i  ^      i 

periments  will  demonstrate  the  presence  of  the 
antibacterial  or  antitoxic  substance  in  the  serum 
of  the  animal  which  possesses  the  immunity.  The 
technic  of  such  experiments  will  be  illustrated  later. 
There  is  another  kind  of  acquired  resistance 
which  properly  may  be  mentioned  here.     It  is  a 


Immun- 
ity. 


DRUG  HABITUATION.  23 

well-known  fact  that  one  may  gradually  accus- 
tom himself  to  enormous  closes  of  morphin,  ar- 
senic, alcohol  and  some  other  drugs.  A  priori,  it 
would  seem  that  this  condition  of  resistance 
should  be  analogous  to  that  which  is  present  in 
antitoxic  immunity.  But,  on  the  contraTy,  the 
seriim  of  a  morphin  or  alcohol  habitue  has  no 
power  of  neutralizing  the  effects  of  morphin  or 
alcohol.  Tlie  conditions  on  which  this  resistance 
depends  are  not  understood. 


CHAPTER  IV. 


HISTORY   AND    DEVELOPMENT. 

Early  Times  and       The    Conception    of   the   nature   of    immunity 

Practices.  ^  .  ,i  "« 

which  was  current  at  one  period  or  another  of 
history  had  some  relationship  to  the  conception 
of  the  etiology  of  diseases  at  those  times.  It  will 
be  remembered  that  at  one  time  diseases  were 
supposed  to  be  imposed  by  an  angry  deity,  and  to 
■  avert  them  various  mysticisms  were  resorted  to, 
such  as  the  utterance  of  incantations  and  the 
wearing  of  talismans.  On  the  other  hand,  a  more 
logical  attempt  to  explain  the  natui'al  immunity 
of  the  Psylli  against  snake  poison  was  made  by 
Pliny,  who  suggested  that  it  might  be  due  to  their 
habit  of  drinking  water  from  wells  in  which  pois- 
onous snakes  dwelt.  This  is  not  unlike  our  pres- 
ent conception  of  active  immunization. 

Von  Behring  quotes  literature  to  show  that 
among  some  primitive  races  of  to-day,  artificial 
immunization  is  carried  on;  a  Mozambique  tribe 
is  said  to  inoculate  against  snake  poison  by  rub- 
bing into  a  small  cutaneous  incision  a  paste  which 
contains  venom.  Probably  non-fatal  quantities 
are  introduced  in  this  wa}^,  resulting  in  the  forma- 
tion of  venom  antitoxin,  a  method  comparable  to 
that  used  in  the  production  of  diphtheria  anti- 
toxin. 

At  a  very  early  period  the  possibility  of  habitua- 
tion to  poisonous  drugs  was  recognized.  We  learn 
that  ]\Iithridates  by  taking  gradually  increasing 
doses  of  poisons  established  in  himself  resistance 


EARLY  CONCEPTIONS.  25 

of  this  sort.  It  is  stated  also  that  he  fed  ducks 
with  poisons  and  then  proposed  to  use  their  blood 
as  an  antidote  (serumtherapy).  The  importance 
of  antidotes  in  the  minds  of  the  ancients  may  be 
appreciated  from  the  fact  that  epidemic  diseases, 
such  as  plague,  cholera  and  smallpox,  were  at  one 
time  considered  as  diie  to  unknown  poisons,  which 
might  be  comparable  in  nature  to  some  known 
poisons,  as  aconite.  Mercury  for  syphilis,  quinin 
for  malaria,  and  salicylic  acid  for  rheumatism 
would  certainly  have  fallen  into  the  category  of 
antidotes,  and  mercury  may  have  been  so  con- 
sidered. 

A  historic  illustration  of  the  treatment  of  dis- 
ease on  a  supposed  etiolo.gic  basis  is  found  in  a 
theory  which  was  prevalent  in  the  seventeenth 
century,  according  to  which  diseases  were  either 
acid  or  basic  in  character,  and  hence  should  be 
treated,  the  one  with  an  alkali,  the  other  with  an 
acid.  Sylvius  considered  plague  to  be  of  acid 
nature  and  administered  alkalies,  while  Etmiiller 
took  the  opposite  view. 

Manifestly,  rational  treatment  and  prophylaxis 
of  the  infectious  diseases  could  not  be  undertaken 
until  their  etiology  was  correctly  understood.  Yet 
here,  as  so  often  happens  in  medicine,  empiricism 
preceded  rationalism.  For  example,  protective 
inoculation  did  not  become  a  principle  until  the 
time  of  Pasteur,  yet  it  had  been  practiced  against 
smallpox  for  centuries,  and  the  method  put  on 
its  present  basis  by  Jenner  long  before  there  was 
any  idea  as  to  the  principles  involved  in  the  pro- 
tection. 

The  belief  that  invisible  "animalcules"  are  able  Micro 
to  cause  morbid  processes  in  man  is  a  very  old 


organisms. 


,    2G  IXFECTIO^^  AXD  IMMUXITY. 

one.  A  passage  from  Yarro  (116-37  B.  C.)  reads 
as  follows :  "There  are  swampy  places  in  which 
grow  animals  never  so  small  which  may  not  be 
recognized  by  the  naked  eye,  and  which  gain  ac- 
cess to  the  body  through  the  air  and  bring  about 
severe  diseases." 
Microscope^  TliG  discovery  and  use  of  the  compound  micro- 
scope in  the  seventeenth  century  disclosed  the 
reality  of  the  minute  living  forms^  which  had  been 
suspected  so  often.  Ivircher,  with  his  first  crude 
microscope  (1646),  examined  the  tissues  of  va- 
rious diseases,  and  was  the  author  of  many  the- 
ories as  to  their  etiology.  It  is  now  believed  that 
the  magnification  of  Kircher's  microscope  was  so 
small  that  many  of  the  "worms"  which  he  saw 
were  really  larger  fungus  cells  and  in  some  in- 
stances the  as  yet  undiscovered  blood  and  pus 
cells. 

Leeuwenhoek  (1632-1723),  a  Dutch  naturalist, 
with  his  compound  microscope  magnifying  1,000 
diameters,  described  accurately  many  microscopic 
forms,  but  made  no  application  of  his  discoveries 
to  medical  problems;  nevertheless,  such  applica- 
tion was  not  wanting,  and  the  succeeding  century 
and  a  half  saw  such  voluminous  descriptions  of 
microbes,  so  many  contradictory  theories  and 
statements  concerning  their  relationship  to  in- 
fections, that  the  "infinitesimally  small"  fell  into 
disfavor  in  many  quarters  as  the  cause  of  diseases. 
The  attractions  and  reasonableness  of  the  theory, 
however,  were  such  that  it  continued  to  gain  ex- 
ponents, and  in  the  early  part  of  the  nineteenth 
century  reached  a  degree  of  definiteness.  In  1855, 
the  great  French  ph}'sician,  Bretonneau,  affirmed 
that  a  specific  germ  was  the  cause  of  every  con- 


MICROBW  SPECIFICITY.  27 

tagious  disease:  "An  epidemic  disease  can  orig- 
inate and  extend  only  through  the  agency  of  the 
germ  producing  it."  Yet  at  this  time  no  infec- 
tion had  been  definitely  proved  to  be  of  microbic 
origin. 

In  1850  Eayer  and  Devaine  made  an  observa-  -^"^hrax. 
tion^,  which  might  have  fallen  into  the  oblivion  of 
many  preceding  ones  had  it  not  been  confirmed  by 
later  investigators.  They  found  "small  filiform 
bodies"  in  the  blood  of  sheep  which  had  died  of 
anthrax,  and  were  ■  naturally  inclined  to  believe 
that  these  forms  caused  the  disease.  Other  stu- 
the  study  of  anthrax,  with  the  result  that  the 
the  study  of  anthrax,  with  the  result  that  the 
small  rods  of  Devaine  were  scientifically  proved  to 
be  its  cause. 

Two  great  minds  dominated  medical  research  Fermentations. 
at  this  time — Pasteur  and  Koch.  Pasteur,  in  his 
early  career  as  a  chemist,  had  had  his  attention 
called  to  the  processes  of  fermentation.  He  re- 
curred to  this  subject  at  a  time  when  the  theory 
of  the  spontaneous  generation  of  small  living 
forms  was  widely  discussed,  and  in  1857-1861 
proved  be3^ond  any  possibility  of  doubt  that  lactic 
acid,  alcoholic  and  butyric  acid  fermentations  were 
due  to  the  action  of  minute  living  cells;  and,  fur- 
thermore, that  *  each  particular  kind  of .  fermenta- 
tion had  its  own  peculiar  microbe  as  the  cause. 
This  was  an  example  of  what  we  term  to-day 
microbic  specificity.  Pasteur  then  applied  what  lyjic^obic 
he  had  learned  about  fermentations  to  the  study  specificity. 
of  the  diseases  of  wines  and  beers.  He  found  their 
causes,  and  devised  a  preventive  measure,  which 
consisted  merel}'  in  the  destruction  of  the  germs 
by  heating  the  wine  to  a  suitable  temperature  be- 


2S 


lyPECTIOX  AXD  IMMUNITY. 


Vaccination. 


AnthraX' 


fore  it  was  stored.  At  the  instance  of  tlie  French 
government,  he  then  studied  certain  diseases  of 
silk  worms.  His  success  in  discovering  their 
causes  and  prevention  must  always  remain  for 
us  one  of  the  landmarks  of  the  world's  progress. 
It  was  during  the  latter  investigations  that  he 
took  up  the  study  of  anthrax.  The  specific  mi- 
crobe having  been  discovered,  and  the  methods  of 
transmission  of  the  malady  having  been  made 
clear  through  investigations  by  both  Pasteur  and 
Koch,  Pasteur  turned  his  attention  to  methods 
of  prevention  and,  if  possible,  of  cure. 

Pasteur  pondered  the  question  of  smallpox  vac- 
cination. He  came  to  believe  that  vaccinia  was 
smallpox,  the  virus  of  which  had  been  attenuated 
by  its  passage  through  the  cow,  and  that  conse- 
quently when  man  was  vaccinated  he  was  inocu- 
lated with  a  benign  form  of  the  disease.  Might 
not  this  be  an  example  of  a  law  which  would  be 
general  in  its  application?  The  protective  inocu- 
lation (active  immunization)  against  the  pleuro- 
pneumonia of  cattle  which  had  long  been  prac- 
ticed gave  encouragement  to  this  hope.  Some 
work  by  Toussaint  was  important  in  the  answer 
to  this  question.  It  was  evident  that  a  weakening 
or  attenuation  of  the  bacteria  or  virus  must  first 
be  obtained  before  it  could  be  safely  injected  into 
animals  for  the  purpose  of  producing  immunity, 
for  if  the.  unaltered  virus  were  injected  the  viru- 
lent infection  would  result.  Accordingly,  Tous- 
saint heated  the  blood  of  a  sheep  which  had  died 
of  anthrax,  to  a  temperature  of  55°  C.  for  ten 
minutes,  then  injected  it  into  a  number  of  sheep. 
Some  of  the  animals  died  of  anthrax,  while  others 
suffered  only  a  mild  attack  from  which  they  re- 


HYDROPHOBIA.  29 

covered;  the  latter  were  found  to  be  immune  to 
a  subsequent  inoculation  with  virulent  blood.  In- 
asmuch, however,  as  some  of  Toussaint's  animals 
had  died  of  anthrax,  Pasteur  concluded  that  there 
was  some  grave  error  in  technic.  He  considered 
that  Toussaint's  method  probably  killed  or  atten- 
uated the  fully-developed  bacilli,  but  did  not  in- 
jure the  spores  of  the  parasite  (Koch  had  pre- 
viously shown  the  existence  of  anthrax  spores). 
After  much  experimentation,  Pasteur  hit  on  the 
plan  of  growing  the  bacillus  at  a  temperature  of 
4:2°  C,  obtaining  'in  this  way  a  culture  of  the 
fully  developed  organism  which  had  a  low  viru- 
lence, but  which  did  not  form  the  dangerous 
spores.  When  sheep  were  inoculated  with  the 
proper  amount  of  this  culture,  which  became 
known  as  anthrax  vaccine,  they  had  a  mild  attack 
of  the  disease,  which  rendered  them  immune  to 
virulent  inoculations. 

With  the  possibility  of  protective  inoculation  Hydrophobia. 
with  a  known  virus  actually  demonstrated,  sim- 
ilar procedures  were  tried  with  other  animal  dis- 
eases of  known  bacterial  etiology,  with  the  result 
that  successful  vaccines  against  chicken  cholera 
and  swine  plague  were  developed.  Somewhat 
later,  having  failed  in  their  attempts  to  discover  ■ 
the  microbes  of  plague  and  cholera,  Pasteur  and 
his  co-workers  turned  to  the  study  of  hydropho- 
bia. All  efforts  to  cultivate  the  virus  from  the 
spinal  cord  of  rabid  dogs,  which  surely  is  its  seat 
in  the  affected  animal,  failed.  The  unique  idea 
then  occurred  to  consider  the  infected  spinal  cord 
as  a  fully  developed  culture  of  the  virus.  It  re- 
mained to  subject  such  a  culture  to  the  proper 
attenuating  conditions  for  the  purpose  of  weaken- 


30 


INFECTION  AND  IMMUNITY. 


Two  Important 
Principles. 


Theories  of 

the  Cause  of 

Immunity. 


Exhaustion 
Theory. 


ing  or  nctnally  destroying  its  virulence  in  order  to 
make  it  tit  for  protective  injections.  Tliis  was  ac- 
complished by  drying  the  cords  in  a  closed  ve?sel 
over  a  hygroscopic  substance  (solid  potassium 
hydroxid),  the  final  virulence  of  the  cord  depend- 
ing on  the  length  of  time  it  had  been  subjected 
to  the  drying  process.  The  technic  of  the  protec- 
tive injections,  the  success  of  which  is  household 
knowledge,  will  be  the  subject  of  later  considera- 
tion. 

Of  primary  importance,  during  this  period,  was 
the  work  of  Koch  on  the  specific  bacteria  of  tu- 
berculosis, cholera,  typhoid  and  the  pyogenic  dis- 
eases; and  not  least  his  improved  methods  of  ob- 
taining pure  cultures  through  the  use  of  solid 
media  (gelatin)  on  j)lates.  Through  his  work  and 
that  of  Pasteur  two  great  principles  had  been 
set  in  motion :  the  microbic  specificity  of  infectious 
diseases,  and  protective  inoculation  in  its  general- 
ized form,  through  the  use  of  attenuated  virus. 

The  scientific  mind  turned  at  once  to  the  in- 
quiry, What  changes  in  an  animal  body  are  re- 
sponsible for  the  immunit}^  which  is  acquired  as 
the  result  of  protective  inoculations?  Also,  upon 
what  properties  of  the  tissues  or  bod}'-  fluids  does 
the  natural  immunity  of  an  animal  depend,  and 
does  the  susceptibility  of  one  species  dejDend  on 
the  absence  of  those  properties  which  characterize 
the  natural  immunity  of  another  species?  Pas- 
teur had  observed  that  if  he  grew  the  microbe  of 
chicken  cholera  in  a  liquid  medium  for  some  time, 
then  removed  the  bacteria  by  filtration,  the  fluid 
became  unfit  for  the  further  growth  of  the  organ- 
ism on  subsequent  reinoculation.  That  is,  the 
nutrient  material  had  been  used  up;  and  he  sug- 


PHAQOCYTO^IH.  31 

gestecl  that  this  is  the  case  in.  the  body  of  an  ani- 
maL  Having  nndcrgone  the  infection,  suitable 
nutrient  material  for  the  microbe  is  used  up,  and 
recovery  ensues.  The  prolonged  absence  of  the 
proper  nutritious  substances  would  account  for 
the  more  or  less  permanent  nature  of  the  acquired 
immunity.  This  conception,  the  exhaustion 
theory,  at  one  time  shared  by  Koch  and  EHebs,  is 
still  represented  in  an  altered  form  by  Baumgar- 
ten,  who  sjDcaks  of  an  unfavorable  culture  medium 
as  representing  the  condition  of  the  immune  body, 
which,  of  course,  is.  broadly  true. 

Chauveau  was  the  aiithor  of  another  historic  Rete'lfon 
theory  of  acquired  immunity  (the  noxious  reten-  Theory. 
tion  theory),  which  maintained  that  during  the 
course  of  a  disease  the  bacteria  produce  substances 
in  the  presence  of  which  they  can  not  develop 
further;  consequently  recovery  takes  place,  and 
the  continued  presence  of  these  noxious  sfubstances 
renders  another  attack  of  the  disease  impossible. 
Although  it  is  true  that  bacteria  do  not  grow  well 
in  their  own  metabolic  products,  theories  of  im- 
munity on  this  and  similar  bases  are  not  in  ac- 
cord with  the  fact  that  immunity  may  be  of  great 
duration,  and  that  it  may  be  conferred  by  the 
injection  of  the  killed  bacteria,  or,  in  some  cases, 
of  their  non-living  soluble  products. 

Metchnikoff  may  be  credited  with  having  first  Phagocytosis. 
offered  a  plausible  explanation  of  natural  resist- 
ance, founded  on  observation.  As  a  zoologist  he 
had  studied  the  .subject  of  intracellular  digestion 
in  the  lower  animals,  and  it  was  while  working  on 
this  problem  that  he  observed  the  fate  of  a  yeast 
fungus  (Monospora),  wliich  caused  epidemics 
among    the    daphnia,  small,  transparent    animals 


32  INFECTION  AND  IMMUNITY. 

•  M-itli  -which  he  was  workiug.  Kear  the  alimentary 
tract,  Avhich  was  tlie  infection  atrium,  some  hirge 
mesoblastic  cells,  which  are  perhaps  analogous  to 
the  white  blood  cells,  were  seen  to  ingest  the  para- 
sites and  dissolve  them.  If  this  took  place  to  a 
sufficient  extent  the  animals  recovered;  if,  how- 
ever, the  infecting  organisms  were  too  numerous 
or  the  reaction  on  the  part  of  the  animal  insuffi- 
cient, the  body  Ijecamc  overwhelmed  with  para- 
sites and  death  resulted.  Since  that  time  Metch- 
nikoff  has  evolved  his  well-known  theory  of  pha- 
2:oc-\i;osis  as  the  essential  factor  in  both  natural 
and  acquired  immunity,  a  theory  which  Pasteur, 
in  his  later  years,  looked  on  with  favor.  "We  may 
speak  of  this  as  the  cellular  theory  of  immunity; 
a  theory  which  has  had  to  imdergo  important 
modications  in  order  to  bring  it  into  accord  with 
new  facts. 
Investigation  Considering  that  natural  or  acquired  immunity 
ties  of  Serums,  must  exist  because  of  certain  qualities  of  the  body 
cells,  or  of  the  body  fluids,  or  possibly  of  both, 
investigators  began  to  make  analyses  of  the  tis- 
sues; and  of  all  the  analyses,  that  which  we  may 
term  the  biologic  has  been  the  most  fruitful.  In 
this  case  biologic  analysis  means  the  detection  of 
reactions  -^'hich  may  occur  when  bacteria  or  their 
products  are  placed  on  contact  with  tissue  cells 
Bactericidal  or  fluids,  either  in  the  living  animal  or  in  test- 
glass  experiments.  The  chief  of  these  are  the  de- 
termination of  the  ability  of  the  serum  of  an  ani- 
mal to  kill  bacteria  or  to  neutralize  bacterial 
toxins.  These  important  investigations,  still  in 
their  infancy,  were  inaugurated  by  the  findings 
of  Fodor,  Nuttall,  N"issen,  v.  Behring  and  Buch- 
ner,  which  showed  that  fresh  defibrinated  blood. 


PROPERTIES  OF  SERUMS.  33 

and  the  blood  serum  of  various  animals,  were  able 
to  kill  bacteria  in  the  reagent  glass.  In  contrast 
to  the  action  of  ordinary  antiseptics,  this  power  is 
often  selective,  killing  one  variety  of  bacterium 
and  leaving  another  unharmed.  This  was  of  enor- 
mous importance,  as  it  seemed  to  identify  the 
factor  on  which  natural  antibacterial  immunity 
depends.  Then  followed  the  discovery  of  Nissen 
and  V.  Behring  (Vibrio  metchniJcovi) ,  and  of 
Bouchard  (B.  pyocyaneus) ,  that  if  an  animal  is 
systematically  injected,  i.  e.,  immunized,  with  a 
micro-organism,  the  power  of  its  serum  to  kill 
the  bacterium  used  in  the  immunization  is  greatly 
increased ;  from  which  it  would  seem  that  acquired 
immunity  depends  on  the  increase  of  powers  which 
are  normally  present  to  a  certain  degree.  These 
observations  have  to  do  with  the  bactericidal  power 
of  serum. 

Further  progress  was  made  through  the  disco v-  Tox/nsand 
ery  that  the  tetanus  bacillus  (Brieger  and  Frankel)  '^"*"®*'"«- 
and  the  diphtheria  bacillus  (Eoux  and  Yersin) 
secrete  each  a  powerful,  specific,  soluble  toxin, 
which  may  be  separated  from  the  bacteria  by  fil- 
tration. Immunization  with  these  bacterium-free 
toxins  was  undertaken  (Behring  and  Kitasato, 
1890)  with  the  familiar  result  of  the  production 
of  the  specific  antitoxins.  Other  investigations  in 
this  direction  soon  showed  the  independence  of 
the  antibacterial  and  the  antitoxic  properties  of 
serums'. 

With  these  facts  in  hand,  the  vigor  with  which 
investigations  have  been  pushed  may  be  readily 
imagined.  The  hope  naturally  prevailed  that  phy- 
sicians might  become  the  masters  of  all  infectious 
diseases,  through  the  possession  of  specific  anti- 


:14  IXFKCTIOX  AM)  HI M I  MTY. 

l>;iet('rinl  and  aiilitoxie  serums.  JJut  raihires,  with 
which  we  are  only  too  familiar,  met  tlie  attempts 
to  prod  nee  adequate  antiserums  for  many  diseases. 
Xevertheless  these  failures,  through  stimulation 
to  closer  study,  have  resulted  in  the  accumulation 
of  much  additional  knowledge  concerning  the 
pathogenic  jn-operties  of  different  bacteria,  the 
nature  of  the  immune  serums  and  the  various  pro- 
tective factors  of  the  body.  Ehrlich  has  evolved 
a  new  theory  of  immunity  from  facts  which  were 
discovered  in  his  laboratory,  the  "side-chain" 
theory,  which  it  is  the  ])urpose  to  utilize  in  the 
interpretation  of  many  reactions  which  will  come 
up  for  consideration. 


CHAPTEK  V. 


NATURAL    IMMUNT'l'Y. 
A.      PROTECTION"  AFFORDED  BY  THE  BODY  SURFACES. 

Virulent  organisms  (e.  g.,  staphylococci  and  The 
streptococci)  exist  normally  on  the  skin  or  be- 
tween the  superficial  horny  cells,  some  exceptional 
circumstance  being  necessary,  e.  g.,  wounds,  to  en- 
able them  to  penetrate  deeper  and  to  cause  disease. 
It  is  evident,  then,  that  the  physiologic  shedding 
of  the  superficial  horny  cells  and  their  continual 
refonuation  at  a  deeper  level  is  a  process  calcu- 
lated to  rid  the  surface  of  the  body  of  many  micro- 
organisms. 

The  question  whether  micro-organisms  can  ever 
penetrate  the  unbroken  skin  has  been  much  dis- 
cussed. Although  experiiuents  have  shown  that 
traumatism  is  not  absolutely  necessary,  clinical 
experience  indicates  that  these  so-called  crypto- 
genetic  infections  are  not  of  ready  occurrence. 
When  they  do  occiir.  the  infection  atrium  is  prob- 
ably one  of  the  glandular  orifices. 

The  SAveat  glands  with  their  ducts,  and  the  hair  Cutaneous 

Orifices. 

follicles  with  their  appended  sebaceous  glands, 
are  vulnerable  points  in  the  defense  which  the 
cutaneous  surface  represents.  Although  they  are 
protected  somewhat  by  the  flow  of  their  excretions, 
especially  in  warm  weather,  and  although  the  en- 
trance of  germs  is  made  more  difficult  by  the  con- 
traction of  the  skin  and  consequent  narrowing  of 
the  orifices  in  cold  weather,  yet  various  incidents 
may   lead   to   the  introduction   and   retention   of 


Subcutaneous 
Connective 


36  INFECTION  AND  IMMUNITY. 

virulent  inicro-orgaiiisms  in  these  structures. 
When  tliis  occurs  there  is  little  difficulty  in  the 
way  of  their  producing  necrosis  of  the  epithelium, 
invading  the  surrounding  tissue  and  causing  a 
pustule,  boil,  carbuncle,  cellulitis,  or  even  a  gen- 
eralized infection.  The  secretion  of  the  sebaceous 
glands  appears  to  be  not  germicidal.  On  the  other 
hand,  the  acid  nature  and  certain  salts  found  in 
perspiration  render  this  fluid  antagonistic  to  the 
development  and  virulence  of  certain  micro-organ- 
isms. 

The  serous  exudate,  and  the  crust  which  forms 
subsequent  to  an  abrasion,  antagonize  infection. 
The  serum  itself  contains  germicidal  substances. 
Avhile  the  crust  mechanically  prevents  microbic 
invasion. 

Soluble  poisons  such  as  aconite  and  bacterial 
toxins  are  not  absorbed  through  the  unbroken  skin. 

Even  after  germs  penetrate  the  epidermis,  the 
Tissue,  subcutaneous  connective  tissue  is  often  an  obstacle 
to  their  further  extension.  The  subcutaneous  in- 
jection of  some  micro-organisms  (e.  g.,  cholera) 
is  tolerated  better  by  animals  than  one  given  into 
the  abdominal  cavity  or  blood  vessels.  We  are 
also  familiar  with  the  benign  course  of  lupus 
compared  with  visceral  tuberculosis;  the  same  is 
true  of  cutaneous  and  visceral  glanders.  This  re- 
sistance is  explainable,  at  least  in  part,  by  the 
rapidity  with  which  new  connective  tissue  forms 
in  the  subcutaneous  tissue,  offering  a  mechanical 
limitation  to  the  infection,  and  by  the  rich  lymph 
supply  which  makes  possible  the  rapid  accumula- 
tion of  bactericidal  lymph  and  of  phagocytic  cells. 
On  the  other  hand,  it  must  be  mentioned  that  in 
some   diseases  the   subcutaneous  tissue  offers  no 


SURFACE  PROTECTION.  37 

perceptible  resistance  to  bacterial  invasion 
(plague),  and  that  toxins  may  be  more  virulent 
when  introduced  into  this  tissue  than  when  in- 
jected into  the  abdominal  cavity  or  the  general 
circulation  ( tetanus ) . 

The  moist  condition  of  mucous  membranes  has  J}"*^""' 
been  found  to  favor  the  multiplication  of  many 
microbes,  although  mucus  itself  is  said  to  atten- 
uate the  virulence  of  some  micro-organisms,  as 
the  pneumococcus ;  mucus,  however,  is  not  actively 
germicidal.  A  laver  of  mucus,  on  the  other  hand, 
is  a  mechanical  protection,  and  its  constant  excre- 
tion is  a  means  of  steadily  removing  bacteria  from 
mucous  surfaces. 

The  conjunctiva  is  protected  against  infection  Conjunctiva. 
by  the  mechanical  interference  of  the  eyebrows, 
eyelashes,  eyelids,  irrigation  of  the  conjunctival 
surface  by  tears  which  carry  germs  through  the 
lachrymal  duct  into  the  nasal  cavity,  the  ability 
of  the  conjunctival  epithelium  to  repair  itself 
rapidly,  and  the  mild  germicidal  action  of  the 
salts  which  are  present  in  the  tears.  These  pro- 
tective agencies,  however,  are  often  surmounted 
by'  micro-organisms,  such  as  the  pneumococcus, 
staphylococcus  and  the  influenza  bacillus.  Many 
soluble  poisons,  aconite,  diphtheria  toxin  and  the 
toxin  of  hay  fever  are  readily  absorbed  from  the 
conjunctiva. 

Compared  with  the  anterior  nares,  the  posterior  Nasal 
are  poor  in  micro-organisms.  This  is  no  doubt 
due  to  the  filtering  of  the  air  by  the  hairs,  the  tor- 
tuosity of  the  channel  causing  dust  and  bacteria 
to  strike  the  walls  where  they  are  held  by  a  moist 
surface,  and  the  action  of  the  ciliated  epithelium 
in  carrying  them  imbedded  in  mucus,  again  to- 


38  IXFECTION  AXD  fMUUXITY. 

ward  the  anterior  nares.  Nevertheless,  the  nasal 
niueou^;  membrane  is  a  common  infection  atrium 
for  streptococci,  staph3'lococci,  diphtheria  and  in- 
tluonza  bacilli,  the  diplococcns  of  epidemic  men- 
ingitis, and,  probabh',  for  other  infectious  agents, 

Mouth.  At  least  thirty  species  of  micro-organisms  flour- 
ish in  the  oral  cavity,  some  of  tliem  being  jjatho- 
genic :  staph3dococci,  streptococci,  pneumococci. 
and  often  diphtheria  bacilli.  They  are  constantly 
removed  Avith  the  saliva,  and  tlu'ougli  the  exten- 
sive desquamation  of  the  epidermis  occasioned  by 
mastication.  Saliva  is  not  germicidal,  but  in- 
liibits  the  growth  and  weakens  the  virulence  of 
some  bacteria.  The  fetid  breath  and  the  sor- 
didity  observed  in  fevers  where  the  mouth  is  dry 
are  attributable  at  least  in  part  to  tlie  lack  oL' 
saliva  with  its  anti-infectious  properties.  The 
great  rapidity  "with  whicli  wounds  of  the  mouth 
lieal  is  a  potent  factor  in  preventing  serious  infec- 
tions. 

Langs.  Micro-organisuis  do  not  readily  reach  tlie  ulti- 
mate ramifications  of  the  bronchioles.  In  ordinary 
respiration  the  velocity  of  the  inspired  air  is  so 
reduced  as  it  nears  the  alveoli  that  the  further 
movements  of  the  gases  is  one  of  gradual  diffusion 
more  than  of  violent  admixture.  Consequently 
there  are  greater  o.p])ortiinities  for  gcrm,>  to  come 
in  contact  with  the  lironchial  walls  where  they 
l)ecome  iml:)edded  in  mucus  with  Avhich  they  may 
be  expelled  by  coughing  and  the  action  of  the 
ciliated  epithelium.  Both  the  alveolar  epithelial 
cells  and  (he  leucocytes  wliicli  enter  the  air  sacs 
and  bronchioles  have  been  shown  to  take  up  bac- 
teria. The  conditions  in  the  lungs  Avhich  favor 
the   develo])inent   of    infections.   l)i'oncl]itis,   pneu- 


HTOMAiJlL  AM)  INTEHTiyEH.  :','.) 

nionJa,  influenza,  tuberculosis,  etc.,  arc  hy  no 
means  clearly  understood.  Variations  in  indi- 
vidual resistance,  here  as  in  other  parts  of  the 
body,  are  certainly  of  great  importance.  It  is 
probable  that  the  lung  is  the  infection  atrium  for 
a  nmnber  of  our  acute  infectious  diseases.  It  has 
been  demonstrated  that  systemic  infections,  as 
with  anthrax  bacilli,  may  be  caused  l)y  the  inhala- 
tion of  the  germs. 

The  gastric  juice,  through  the  hydrochloric  stomach. 
acid  it  contains,  is  able  to  kill  anthrax,  typhoid, 
tubercle  bacilli,  cholera  vibrio  and  other  organ- 
isms. Clinical  and  experimental  evidence  shows 
that  this  power  is  often  inadequate,  virulent 
micro-organisms  reaching  the  intestines  in  spite 
of  it  (typhoid,  cholera,  dysentery,  tuberculosis, 
etc.).  It  is  probable  that  bacteria  in  the  stomach 
are  often  protected  against  the  action  of  the  gas- 
tric juice  to  some  extent  by  being  imbedded  in 
solid  particles  of  food.  Certain  acidophilic  germs, 
as  Avell  as  yeasts  and  torulge,  seem  to  flourish  in  the 
gastric  secretions;  these  are  largely  non-patho- 
genic, but  the  regularity  with  which  peritonitis 
follows  perforating  wounds  of  the  stomach  indi- 
cates that  it  probably  always  contains  pathogenic 
bacteria,  though  it  may  be  only  their  temporary 
habitat.  The  gastric  juice  may  render  some  bac- 
teria harmless  by  digesting  their  toxins;  one 
gram  of  the  gastric  juice  of  a  dog  will  neutralize 
fifty  fatal  doses  of  diphtheria  toxin,  or  10,000  of 
tetanus  toxin,  using  the  guinea-pig  as  the  test 
animal.  On  the  other  hand,  the  toxin  of  the  bacil- 
lus of  botulism  (causing  a  form  of  meat  poison- 
ing) seems  to  .be  uninfluenced  by  the  stomach  eon- 
tents,  as  the  development  of  the  intoxication  indi- 


40  INFECTIOX  AND  IMMUNITY. 

cates.  Vomiting  is  often  a  means  of  ridding  the 
stomacli  of  toxic  substances,  including  bacteria. 
The  stomach  itself  is  exceptionall}^  free  from  in- 
fections. 
Intestines.  Tlie  bile  is  moderately  bactericidal  for  some 
germs,  but.  on  the  whole,  the  intestinal  secretions 
have  low  germicidal  powers;  this  is  indicated  by 
the  fact  that  the  colon  contains  many  more  bac- 
teria than  the  duodenum.  On  the  other  hand, 
the  pancreatic  juice  destroys  some  toxins  (diph- 
theria, tetanus)  more  powerfully  even  than  the 
gastric  juice.  This  ability  of  the  pancreatic  juice 
to  destroy  toxic  bacterial  products  may  explain  the 
more  frequent  occurrence  of  enteritis  in  the  ileum 
than  in  the  duodenum.  The  bile  also  has  a  neu- 
tralizing power  for  some  toxins.  Although  a  num- 
ber of  pathogenic  bacteria  inhabit  the  intestinal 
tract  (colon  bacillus,  streptococci,  etc.),  they  do 
not  often  set  up  inflammatory  processes  in  the 
adult.  The  tissues  become  accustomed  to  their 
presence.  The  pathogenic  bacteria  which  do  not 
normally  exist  in  the  intestines  are  those  which, 
on  introduction,  are  most  likely  to  cause  disease 
(typhoid,  cholera,  dysentery,  etc.).  The  intesti- 
nal tract  of  the  infant,  on  the  other  hand,  is  fre- 
quently attacked  by  some  micro-organisms  (strep- 
tococcus, colon  bacillus,  bacillus  pyocyaneus), 
which  in  the  same  locality  in  the  adult  appear 
harmless.  The  fact  that  many  individuals  are  not 
stricken  in  an  epidemic,  in  which  all  are  equally 
exposed  to  infection,  points  to  the  probability  that 
pathogenic  organisms  (t^^hoid.  cholera  and  dys- 
entery) often  traverse  the  intestinal  canal  without 
inducing  disease.  ISraturally,  microbes  are  elimi- 
nated in  enormous  quantities  in  the  feces,  and  in 


INFLAMMATION.  41 

inflammatory  states  this  elimination  is  increased 
by  diarrhea.  It  is  also  not  to  be  forgotten  that  the 
intestinal  tract  is,  to  a  considerable  extent,  a 
lymphoid  organ,  and  that  consequently  in  the 
presence  of  infection  enormous  quantities  of 
phagoc}d:es  can  quickly  be  called  into  action. 

The  protective  properties  of  the  genito-urinary 
surfaces  are  not  different  in  principle  from  those 
already  mentioned  (vaginal  acidity,  urinary  irri- 
gation) . 

B.    THE  PROTECTIVE  NATURE  OF  INFLAMMATION". 

Although  there  are  many  chemical  and  physical   Nature  of  _ 

,  ,  .   ,  .     r,  ,•  ^    '^      .         Inframmation. 

agents  which  may  cause  miiammation,  we  are  in- 
terested here  only  in  those  of  an  infectious  na- 
ture. 

Inflammation  may  be  considered  a?  a  reactive 
condition  on  the  part  of  the  tissues,  which  devel- 
ops in  response  to  the  action  of  some  injurious 
agent.  The  process  may  be  beneficial  in  some  in- 
stances, while  in  others  it  may  be  pernicious  from 
the  beginning  to  the  end.  The  thickening  of  the 
endothelium  of  the  cerebral  vessels  as  one  sees  it 
in  syphilis  is  a  progressive,  reactive  change  which 
in  no  sense  can  be  of  benefit  to  the  individual,  and 
which  can  have  no  conceivable  function  in  over- 
coming the  s;\nphilitic  infection.  Likewise,  the  new 
formed  connective  tissue  seen  in  alcoholic  cirrho- 
sis of  the  liver  is  of  no  benefit  to  the  hepatic  tissue, 
though  it  may  serve  in  some  degree  to  protect  the 
liver  cells  from  the  alcohol  which  continues  to  be 
ingested.  In  an  ulcer  of  the  cornea  the  presence 
of  serum  and  of  leucocytes,  as  well  as  the  prolifer- 
ation of  connective  tissue,  may  be  the  sine  qua  non 
for  the  healing  of  the  ulcer,  vet  the  resultinsf  scar 


41  lyFKCTlOX  AXD  IMMUXITY. 

may  liTeatiy  i!iii>air  the  vision.  The  intiainmation 
ill  the  instances  cited  is  injurious  because  of  tlie 
functional  importance  of  the  tissues  involved.  On 
the  other  hand,  an  extensive  scar  Avhich  has 
formed  in  tissues  of  less  functional  importance, 
as  in  the  skin  and  suhcutaneous  tissue,  may  he 
harmless. 

It  is  then  to  he  recognized  that  there  are  certain 
consequences  of  the  inflammatory  reaction,  the 
seriousness  of  which  depends  on  the  situation, 
severity,  duration  and  extent  of  the  ])rocess.  and 
that  these  consequences  are  independent  of  any 
]'»rotective  function  the  inflammation  may  have 
exercised. 
Variations  in        The  amouut  and  character  of  the  reaction  are 

tfc«  Reactions. 

subject  to  many  variations,  depending  on  a  num- 
ber of  conditions : 

1.  It  varies  Avitli  the  nature  of  tlie  microbe. 
Xon-pathogenic  organisms  induce  little  more  in- 
flammation than  so  many  minute,  inanimate, 
non-toxic  particles.  The  tubercle  bacillus  causes 
especially  the  formation  of  connective  tissue, 
giant  cells  and  the  accumulation  of  lymphoid 
cells,  aside  from  some  retrogressive  changes  char- 
acteristic of  the  disease.  Organisms  similar  to 
the  streptococcus  and  pneumococcus  lead  to  the 
formation  of  ]-)us  and  fibrin,  to  the  accumulation 
of  serum  and  of  polymor])honuclear  leucocytes 
more  than  mononuclears,  Avhereas  the  prolifera- 
tion of  fixed  tissue  elements  is  secondary.  The 
tetanus  bacillus  alone  causes  almost  no  local  in- 
flammatory change. 

2.  The  reaction  is  influenced  by  the  virulence 
of  a  particular  bacterium.  A  streptococcus  which 
has  lost  its  virulence  is  disposed  of  liy  the  animal 


PIIA  aoOYTOSfS.  43 

tissues  with  a  niiniiniu)]  tissue  reaction,  perliaps 
no  more  than  slight  congestion  and  edema  and 
the  wandering  in  of  a  few  leucocytes;  one  of  liigh- 
er  virulence  causes  an  intense  reaction,  mani- 
fested by  congestion,  edema,  hemorrhages,  necro- 
sis and  pus  formation;  then  streptococci  of  such 
great  virulence  that  they  destroy  life  in  the  course 
of  a  few  hours  are  occasionally  encountered  in 
wound  infections  and  in  peritonitis,  having  in  the 
meantime  elicited  a  minimum  inflammatory  reac- 
tion. 

3.  It  has  a  relation  to  the  resistance  or  the  nat- 
ural immunity  of  the  individual.  Metchnikoff, 
in  particular,  has  shown  that  animals  of  high  re- 
sistance to  a  particular  microbe  destroy  the  germ 
quickly  by  phagocytosis  (the  ingestion  of  parti- 
cles by  cells,  especially  the  leucocytes),  while  in 
susceptible  animals  the  accumulation  and  activity 
of  phagocytic  leucocytes  are  deficient. 

The  occurrence  of  leucocytes  in  inflammatory  Leucocytes. 
conditions  is  so  characteristic  that  one  naturally 
seeks  to  associate  their  presence  with  some  in- 
fluence which  is  exerted  by  the  toxic  substance  or 
the  bacteria  which  cause  the  inflammation.  It  is 
a  long-known  fact  that  some  microbes  attract  one 
kind  of  leucocyte,  that  others  attract  another 
kind,  and  that  in  still  other  instances  the  leuco- 
cytes appear  to  be  either  uninfluenced  or  actually 
are  repelled  by  the  infecting  agent. 

Tliis  phenomenon  of  living  cells  moving  toward  chemotaxis. 
or  away  from  certain  other  cells  or  substances  is 
termed  chemotaxis ;  the  former  is  positive,  the  lat- 
ter negative,  chemotaxis.  There  is  a  somewhat 
general  law,  but  one  to  which  exceptions  exist, 
that,  regardless  of  the  microbe  involved,  the  more 


44  INFECTION  AND  IMMUNITY. 

acute  the  inflnnimatorv  process  the  more  do  poly- 
inori)hoiiuc]ear  leucocytes  accumulate,  while  in 
the  more  chronic  infections,  with  much  connec- 
tive tissue  formation,  the  mononuclear  leucocytes 
predominate.  Thus  in  tuberculosis  one  finds 
lymjDhocytes  and  plasma  cells — mononuclears — 
predominating  greatly  over  the  polymoi'phonu- 
clears.  In  the  acute  purulent  infections,  on  the 
other  hand — streptococcus,  staphylococcus,  pneu- 
mococcus — the  latter  type  of  leucocyte  predomi- 
nates, the  mononuclears  being  fewer  and  remain- 
ing at  a.  distance  from  the  center  of  action.  There 
is  reason  to  believe  that  the  mononuclear  leuco- 
c^"tes  play  an  important,  though  perhaps  indirect, 
role  in  the  formation  of  the  connective  tissue. 
Phagocytosis.  The  ingestion  of  particles  by  living  cells,  phago- 
cytosis, is  a  property  which  many  cells  possess. 
Although  micro-organisms  and  inanimate  parti- 
cles are  sometimes  found  in  epithelial  cells,  cer- 
tain of  the  mesoblastic  cells  have  this  function 
pre-eminently :  Pol3^morphonnclear  leucoc3i;es, 
large  mononuclear  leucocytes  (lymphocytes), 
ameboid  connective  tissue  and  endothelial  cells. 
Of  these  the  pol^miorphonuclear  leucoc}d:es,  the 
microphages  of  Metchnikoff,  have  the  greatest 
phagocA'tic  power;  the  others,  the  macrophages, 
are  more  exceptionally  phagocytic.  Now,  the 
mere  ingestion  of  the  bacteria  by  such  cells  would 
not  be  of  necessity  injurious  to  the  microbes;  in- 
deed, opponents  of  MetchnikofE's  phagocytic 
theory  of  immunity  hold  that  phagocytosis  by 
wandering  cells  may  be,  and  often  is,  pernicious, 
in  that  the  cells  may  return  to  the  circulation  and 
spread  the  infection  to  other  parts.  But  when  we 
learn  that  after  ingesting  the  bacteria  the  phago- 


PLASMA,  SERUM   AND   FIBRIN.  45 

cytes  are  often  able  to  kill  and  digest  them,  it  is 
realized  that  the  process  may  be  a  genuine  pro- 
tective factor.  This  being  true,  the  importance  of 
positive  chemotaxis  in  recovery  from  an  infection 
becomes  manifest.  It  is  also  represented  that 
phagocytic  cells  have  the  power  of  excreting  their 
germicidal  substances  into  the  plasma  and  serum 
and  lending  to  the  latter  a  bactericidal  power. 
Furthermore,  it  is  held  that  they  may  absorb  liquid 
poisons,  bacterial  toxins,  and  in  some  manner  de- 
stroy their  toxicity.  As  shown  later,  these  are  es- 
sential points  in  the  j)hagocytic  theory  of  immun- 
ity. 

Serum,  even  when  entirely  free  of  leucocyte?,  influence  of 
has  bactericidal  powers;  it  need  not  be  discussed  serum. 
at  present  whether  this  power  exists  primarily  in 
the  serum  or  is  one  conferred  on  it  by  the  leuco- 
cytes. In  view  of  its  presence,  however,  it  is  evi- 
dent that  the  serous  exudate  which  is  usually 
present  in  inflammations,  especially  the  acute, 
may  be  of  influence  in  combating  the  infection. 
Serum  often  contains  natural  antitoxins,  and,  in 
addition,  it  may  be  of  value  in  lessening  the  tox- 
icity of  poisons  by  diluting  them  and  aiding  in 
their  elimination. 

The  abundant  deposit  of  fibrin  seen  in  some  in-  Fibrin. 
fiammations  is  of  mechanical  value  by  hemming 
in  the  infection  and  in  offering  a  barrier  to  the 
rapid  diffusion  of  toxins.  We  are  all  familiar 
with  the  part  pla3^ed  by  fibrinous  and  fibrous  ad- 
hesions in  preventing  a  localized  peritonitis  from 
becoming  generalized.  In  prolonged  inflamma- 
tions fibrin  furnishes  a  ground  substance  into 
which  new  connective  tissue  and  vessels  grow  (or- 
iranization). 


4t;  lyFECTIOX  AM)  IMMi'MTY. 

Inflammatory        Tlio  iicw  fomiefl  coiinective  tissue  seen  in  many 

Connective     .  •    n       ,i  i  •  •       i.    i      ' 

Tissue,  inllamniations,  especially  tlie  clironic,  as  m  tuher- 
oulosis  and  actinomycosis,  offers  an  important 
l)arrier  to  the  extension  of  an  infection.  Perhaps 
no  l)etter  example  of  this  conkl  he  cited  than  the 
■  dense  tissue  which  forms  aroinid  a  luticMvulous 
sinns  or  ahscess. 

To  Slim  up.  the  inllamiiiatory  reaction  antago- 
nizes infections.  1.  mechanically,  through  the 
formation  of  new  connective  tissue  around  the 
focus,  and  dense  accumulations  of  leucocytes  and 
iihrin;  2,  through  the  bactericidal  and  antitoxic 
actions  of  the  lymph  and  serum;  3,  through  the 
]diagocytic  action  of  amehoid  cells. 

The  value  of  hot  applications  in  local  inflam- 
mations, in  that  they  increase  congestion,  Avhich 
hastens  the  exudation  of  plasma  and  leucocytes 
and  the  proliferation  of  cells,  finds:  a  logical  ex- 
planation in  view  of  the  facts  mentioned.  Also 
increase  in  local  temperature  probably  favoi-s 
chemical  actions.  The  special  features  of  the 
phagocytic  theory  of  immunity  are  considered  in 
a  later  chapter.  For  many  details  in  regard  to 
inflammation,  the  reader  is  referred  to  the  classic 
article  of  Adami  on  this  subject  in  the  first  vol- 
ume of  x\llbutt's  System  of  Medicine. 

C.    THE    ANTIBACTERIAL    AND    THE    ANTITOXIC 
NATURE    OF    NATURAL    IMMUNITY. 

In  a  previous  page  it  has  been  stated  that  nat- 
ural immunity  may  be  either  antibacterial  or  anti- 
toxic. We  have  seen  that  the  protection  afforded 
by  the  body  surfaces  may  be  effective  against  both 
microbes  and  their  toxins,  and  that  local  inflam- 
matory processes,  although  most  certainly  antago- 


NATUMAfj   .\NTII',.\(!Ti:h'l.\L   IMMIMTV.       47 

nizing  tIic   hacicna,   mn}-  at  the  same  time  have 
some  antitoxic  value. 

The  term  natural  irnmimity,  however,  as  indi-  JJ^J-barteriafl 
cated  ill  the  first  chapter,  lias  a  peculiar  applica-  immunity. 
tion  to  tlio  natural  resistance  of  some  species  or 
races  of  animals  to  infections  to  which  other  spe- 
cies or  races  are  susceptible;  and  to  an  unusual  in- 
dividual resistance,  often  seen  in  members  of  a 
given  race  or  species.  This  condition  depends  on 
properties  residing  in  the  tissues  or  fluids  of  the 
liody,  and  consequently  is  independent  of  any  pro- 
tection Avhicli  the  body  surfaces  afford.  Its  pres- 
ence is  demonstrated  in  the  most  striking  man- 
ner by  tlie  experimental  method,  when  microbes 
or  toxins  are  injected  directly  into  the  tissues  or 
circulation.  At  the  same  time  every-day  observa- 
tion provides  many  examples. 

In  determining  the  antibacterial  nature  of  im- 
munity in  a  given  case  there  are  two  conditions 
which  must  be  proved :  1,  that  the  body  cells  or 
fluids  are  able  to  destroy  the  microbe,  and  that 
this  power  is  s.uJ0Liciently  strong  to  make  it  reason- 
able that  the  immunity  depends  on  it;  2,  that  the 
immunity  does  not  depend  on  non-susceptibility 
to  a  possible  toxin  of  the  microbe,  nor  on  a  nat- 
urally existing  antitoxin. 

To  prove  the  first  condition,  three  procedures 
may  be  resorted  to :  First,  the  microbes  are  in- 
jected into  the  subcutaneous  tissue,  the  peritoneal 
cavity  or  the  blood  vessels.  If  the  animal  does 
not  become  ill  after  a  dose  which,  in  proportion  to 
weight,  is  pathogenic  for  some  other  test  animal, 
an  immunity  is  indicated.  At  a  proper  interval 
all  the  tissues  and  fluids  are  examined  to  deter- 
mine the  fate  of  the  microbes.     This  may  be  done 


48  INFECTION  AND  IMMUNITY. 

by  staining  the  fluids  and  cells  for  bacteria  and 
examining  with  the  microscope,  or  by  inoculating 
culture  tubes  with  tlie  fliiids,  the  growth  or  non- 
gro^^ih  of  colonies  determining  wliether  or  not  the 
microbe^^  have  disappeared.  Examinations  of  this 
nature  often  disclose  the  fact  that  many  of  the 
bacteria  have  been  phagocytized  by  the  leucocytes, 
while  others  have  apparently  succumbed  to  the 
germicidal  action  of  serum  or  plasma.  It  is  often 
desirable  to  determine  the  extent  to  which  mi- 
crobes are  eliminated  through  the  excretions 
(urine  or  feces)  ;  this  is  best  done  by  the  culture 
method,  but  is  a  difficult  technical  problem. 

Second,  the  animal's  serum  or  plasma  may  be 
mixed  with  a  suspension  of  the  microbes  in  a 
number  of  test  tubes,  using  varying  amounts  of 
serum  with  constant  amounts  of  the  bacteria  in 
the  different  tulies.  and  at  a  f^ubsequent  period, 
from  tbree  to  twenty-four  hours  later,  cultures 
are  made  from  these  mixtures  to  determine  the 
bactericidal  power  of  the  serum.  Tlie  numbers  of 
colonies  which  appear  in  these  cultures,  minus  the 
number  which  appear  when  ?erum  is  not  added,  is 
an  index  of  the  bactericidal  power  of  the  serum. 
If  this  power  is  found  to  be  high,  it  is,  in  the  pres- 
ent state  of  our  knowledge,  considered  as  pre- 
sumptive evidence  that  the  natural  immunity  of" 
the  animal  depends  on  it.  It  is,  nevertheless,  a 
fact  that  the  antibacterial  immunity  of  an  animal 
does  not  always  go  hand  in  hand  with  the  bac- 
tericidal power  of  its  serum.  A  well-loiown  illus- 
tration of  this  is  the  following:  Both  the  dog  and 
the  rat  have  a  rather  high  degree  of  immunity 
against  infections  witli  the  anthrax  bacillus;  vet 
it  has  been  found  tliat  the  serum  of  the  dog  has 


NATURAL  ANTITOXIC  IMMUNITY.  49 

almost  no  bactericidal  effect  on  this  microbe,  while 
that  of  the  rat  has  a  very  strong  effect.  At  the 
same  time  we  should  remember  that  the  bacterici- 
dal power  of  the  serum  does  not  necessarily  repre- 
sent the  entire  antibacterial  function  of  the  body. 
In  the  serum  we  have  none  of  the  body  cells,  and 
especially  none  of  the  phagocytes,  the  destructive 
action  of  which  on  some  bacteria  is  well  known. 

Third,  it  is  now  possible  to  perform  test-tube 
experiments  with  the  leucocytes  of  an  animal, 
whereby  the  phagocytic  power  of  these  cells  for  a 
given  microbe  may  be  determined.  This  may  be 
done  by  counting  in  stained  specimens  the  num- 
ber of  bacteria  which  are  englobed;  or  the  bac- 
tericidal power  of  the  leucocytes  may  be  deter- 
mined approximately  by  performing  the  culture 
experiments  described  in  the  preceding  paragraph, 
in  this  instance,  however,  substituting  fresh  defib- 
rinated  blood  for  the  serum.  If  the  bactericidal 
power  of  the  defibrinated  blood  (containing  leu- 
coc5rtes)  is  greater  than  that  of  the  serum  alone, 
the  effect  of  the  leucoc}i:es  becomes  apparent. 
This  receives  further  consideration  in  the  chapter 
on  phagocytosis. 

At  a  time  when  the  antitoxic  action  of  serums  Alexins. 
was  not  appreciated,  Buchner  gave  the  name  of 
alexins  (from  the  Greek,  aX^^eiv,  to  ward  off)  to 
the  protective  substances  of  the  serum,  i.  e.,  to  the 
bactericidal  substances,  making  the  observation 
that  they  were  very  labile  substances,  losing  their 
power  spontaneously  in  a  few  days  when  exposed 
to  the  air  and  light,  or  when  they  were  heated  to 
55  C.  for  thirty  minutes. 

In  determining  the  presence  or  absence  of  anti-  ^^^»f^K 
toxic  immunity,   the  toxin   of  the    microbe,    of  immunity. 


50  INFECT  I  Oy  AND  IMMUNITY. 

course,  must  first  be  in  hand.  The  methods  of  ob- 
taining toxins  will  be  referred  to  later.  If  the 
animal  resists  a  dose  of  toxin  which,  in  proportion 
to  weight,  produces  disease  in  some  other  suscepti- 
ble animal,  the  tissues  or  fluids  of  the  first  animal 
may  contain  antitoxin.  It  will  be  indicated  later 
how  this  result  may  be  obtained  even  without  the 
jDresence  of  antitoxin,  the  immunity  being  due  to 
some  other  obscure  cause.  If  the  resistance  is 
referable  to  the  presence  of  antitoxin,  the  latter 
may  be  detected  in  the  following  manner:  The 
animal  is  bled,  its  serum  collected  from  the  clot, 
then  mixtures  of  the  serum  and  of  the  toxin  are 
injected  into  animals  of  known  susceptibility  for 
the  toxin.  If  the  test  animal  is  in  this  way  pro- 
tected from  an  otherwise  fatal  dose  of  the  toxin, 
it  is  evidence  that  the  serum  contains  an  antitoxic 
substance. 

Following  this  method  of  experimentation,  if 
antibacterial  properties  are  found  to  the  exclusion 
of  antitoxic,  the  immunity  is  considered  to  be  an- 
tibacterial ;  and -with  the  converse  result  it  is  anti- 
toxic. It  is,  of  course,  conceivable  that  in  a  given 
case  it  might  be  both  antitoxic  and  antibacterial. 
In  dealing  with  diseases  of  which  the  specific  mi- 
crobe is  known  and  cultivated,  the  existence  of 
antibacterial  or  of  antitoxic  substances  can  usual- 
ly be  found  by  the  methods  described.  If  the  eti- 
ologj  is  unknown,  as  in  scarlet  fever,  measles, 
s}qohilis,  etc.,  that  is,  if  the  virus  and  its  toxin  can 
not  be  obtained  in  quantities,  the  nature  of  the 
resistance  is  not  at  present  open  to  determination. 

Examples  are  kno"^vn  in  which,  in  spite  of 
rather  high  resistance  on  the  part  of  the  animal, 
it?   serum   contains  neither   strong  antitoxic   nor 


Relative 
Immunity. 


NON-8  USCIJ/'Tf/ifLITY.  5 1 

bactericidal  properties.  This  relationship  exists 
between  a  number  of  animals  and  such  bacteria 
as  the  pneumococcus,  staphylococcus  and  strepto- 
coccus. It  is  possible  that  the  phagocytes  are  im- 
portant factors  in  immunity  to  these  infections. 

It  is  seldom  that  natural  resistance  is  absolute. 
Pasteur  found  that  the  great  immunity  of  the 
chicken  for  anthrax  could  be  overcome  by  im- 
mersing the  animal  in  cold  water,  the  reduction 
in  body  temperature  supposedly  decreasing  the  re- 
sistance. It  was  stated  in  a  previous  chapter  that 
physical  exhaustion,  hunger  and  exposure  to  cold 
may  also  reduce  natural  resistance.  Pestilence 
and  famine  often  go  hand  in  hand. 

Similarly,  antitoxic  immunity  usually  is  rela- 
tive. The  chicken,  which  withstands  a  large  quan- 
tity of  tetanus  toxin  when  injected  into  the  skin, 
muscles  or  circulation,  succumbs  when  the  toxin 
is  injected  directly  into  the  nervous  tissue.  As 
an  illustration  of  natural  immunity  to  toxins, 
the  following  table  serves  a  good  purpose.  The 
horse  is  the  most  susceptible  animal  for  tetanus 
toxin.  If  the  minimimi  fatal  amount  for  one  gram 
of  horse  weight  is  taken  as  a  unit,  this  scale  of  re- 
sistance for  some  other  animals  is  obtained 
(Knorr)  : 

For  1  gram  of  guinea-pig  weight 2  units  are  fatal 

For  1  gram  of  goat  weight 4  units  are  fatal 

For  1  gram  of  mouse  weight 13  units  are  fatal 

For  1  gram  of  rabbit  weight 2,000  units  are  fatal 

For  1  gram  of  chicken  weight 200,000  units  are  fatal 

In  view  of  the  high  immunity  of  the  chicken  tib^'ft"**^®"' 
against  tetanus,  one  may  be  led  to  suppose  that  its 
serum  would  contain  a  large  amount  of  antitoxin, 
yet  experiments  show  that  it  possesses  practically 
no  tetanus  antitoxin.  This  fact  suggests  that 
there   is    a   distinct   type    of    natural    immunity 


52  INFECTION  AND  IMMUNITY. 

which,  it  is  tliouglit,  may  be  independent  of  both 
the  antibacterial  and  the  antitoxic  properties  of 
tlie  body. 

Receptoi^s!  ^^  ^^  ^^^^  thought  that  the  toxic  elements  of  bac- 
teria are  chemical  substances  (very  complex, 
surely)  which  are  able  to  injure  the  tissues,  i.  e., 
to  cause  disease,  only  by  entering  into  chemical 
union  with  substances  which  the  cells  contain. 
■  Such  chemical  substances  of  groups  pertaining 
to  the  cells  will  be  referred  to  later  under  the 
name  of  cell  receptors.  Accordingly,  if  the  cells 
of  an  animal  do  not  possess  groups  or  receptors 
which  are  capable  of  forming  a  chemical  union 
with  the  toxin,  the  latter  would  be  unable  to  pro- 
duce injury,  i.  e.,  the  animal  would  be  immune 
even  in  the  absence  of  all  bactericidal  or  antitoxic 
properties.  This  condition,  however,  is  not  one 
which  is  capable  of  experimental  demonstration, 
at  least  at  present,  but  the  conditions  point  irre- 
sistibly to  its  existence  in  some  cases. 

We  are  accordingly  led  to  the  conclusion  that 
immunity  to  toxins  is  not  in  all  cases  antitoxic, 
in  the  sense  that  the  serum  contains  demonstrable 
antitoxin;  and  likewise  that  immunity  to  bacteria 
is  not  in  all  cases  antibacterial,  in  the  sense  that 
the  serum  contains  substances  which  are  able  to 
kill  the  bacteria  in  test-tube  experiments.  N'on- 
susceptibility  and  phagoc5i;osis  may  be  of  impor- 
tance in  resistance  of  this  t}'pe. 
Importance  of       There  is  another  factor,  however,  which  mav 

the  Tissue  ti,  ,i  p         ,         i-  •,       •      \ 

Attacked,  throw  light  on  the  type  ot  natural  immunity  ]ust 
considered.  We  know  that  tetanus  toxin  causes 
tetanus  through  its  power  of  uniting  with  the 
nerve  cells,  and  we  may  consider  that  tetanus  is 
a  very  fatal,  disease,  primarily  because  of  the  vital 


NUMMARY.  53 

nature  of  the  tissue  which  it  attacks.  Now,  if  the 
toxin,  instead  of  uniting  with  the  cells  of  a  vital 
organ,  were  to  combine  with  cells  of  less  impor- 
tance to  the  economy,  as,  for  example,  the  cells 
of  the  subcutaneous  tissue,  it  is  probable  that  we 
should  have  no  tetanus.  In  some  of  the  lower  ani- 
mals there  is  reason  to  believe  that  the  toxin  of 
tetanus  does  unite  with  such  tissue  (Metchnikoff). 
Eoux  and  Borrel  believe  that  the  greater  degree  of 
immunity  which  the  rabbit  has  over  the  guinea- 
pig  is  due  largely  to  the  fact  that  the  rabbit's 
liver  is  able  to  fix  a  great  deal  of  the  toxin.  And 
Metchnikoff  has  found  that  the  liver  of  the  scor- 
pion, which  has  an  absolute  immunity  to  tetanus, 
absorbs  the  toxin  and  retains  it  for  months. 

By  way  of  summary,  then,  we  may  say  that  the  Summary. 
natural  blood  immunity  and  tissue  (histogenic, 
Behring)  immunity  depend  on  the  following  fac- 
tors: Bactericidal  and  antitoxic  powers  of  the 
serum  and  plasma,  the  destructive  effect  of  the 
cells,  especially  the  phagocytes,  on  both  bacteria 
and  toxins;  a  possible  absolute  non-susceptibility 
in  some  cases  (the  absolute  non-existence  of  suit- 
able cell  receptors)  ;  the  overwhelming  distribu- 
tion of  the  suitable  receptors  for  the  toxin  in  or- 
gans of  less  vital  necessity  for  the  individual,  thus 
diverting  it  from  more  important  organs. 

In  order  that  a  pathogenic  organism  produce  a 
progressively  fatal  disease  in  a  susceptible  animal, 
the  following  obstacles  must  be  surmounted:  The 
strong  defenses  of  the  body  surfaces  must  first  be 
overcome;  a  local  inflammatory  reaction  which 
may  have  been  excited  must  first  prove  itself  to  be 
inadequate  for  the  limitation  of  the  infection; 
there  must  be  an  insufficient  supply  or  insufficient 


54  INFECTION  AND  IMMUNITY. 

activity  of  antiruicrobie  and  antitoxic  processes  in 
the  body  fluids  and  cells. 

In  view  of  the  wide  variations  in  the  nature  of 
different  infectious  agents,  it  is  possible  that  the 
defensive  means  wliieh  would  counteract  one 
might  be  inadequate  for  another;  and  inasmuch 
as  animals  appear  to  differ  as  much  in  the  charac- 
ter of  their  defensive  as  microbes  do  in  their  of- 
fensive powers,  there  is  abundant  room  for  the 
display  of  the  various  phenomena  of  natural  im- 
munity and  of  natural  susceptibility  with  which 
we  have  become  familiar. 

OTHER    PROPERTIES    OF    NORMAL    SERUMS. 

Hemolysis.  In  addition  to  the  bactericidal  and  antitoxic  ac- 
tion of  many  normal  serums,  they  often  possess 
other  characteristics  which  are  of  the  highest  in- 
terest in  the  study  of  immunity.  In  earlier  days 
it  had  been  noted  that  the  transfusion  of  blood 
from  one  species  to  another  was  often  fatal  to  the 
injected  animal.  Later  investigations  showed 
that  this  w^as  due  to  toxic  substances  in  the  trans- 
fused blood ;  substances  which,  above  all,  de- 
stroyed the  red  blood  cells  of  the  injected  animal. 
This  action,  in  which  the  hemoglobin  is  dissolved 
out  of  the  red  blood  cells,  may  be  reproduced  m 
test-tube  experiments  .by  mixing  the  blood  cells  of 
one  animal  with  the  serum  of  another  which  is 
toxic  (e.  g.,  rabbit  blood  -j-  goat  serum).  This  is 
the  phenomenon  of  hemolysis,  and  the  appearance 
of  such  a  tube  is  exactly  like  that  seen  when  blood 
is  mixed  with  distilled  water  or  even  with  tap 
water;  i.  e.,  it  is  a  laking  of  the  blood,  it  loses  its 
opacity  and  assumes  a  beautiful  cherry-red  color. 
The  serum  of  practically  every  species  contains  a 


HEMOLYSINS,  ETC. 


55 


hemolytic    substance    (a    serum    hemolysin)     for 
some  kind  of  erythrocyte. 

Some  serums  also  contain  toxic  agents  for  other  Cytotoxins. 
cells;  they  are  generally  called  serum  cytotoxins. 
The  serum  of  the  eel  not  only  contains  a  strong 
hemolysin,  or  hemotoxin,  but  also  a  powerful 
poison  for  nervous  tissue,  neurotoxin.  Similarly 
we  have  normal  leucotoxins  for  leucocytes,  nephro- 
toxin  for  kidney  tissue,  etc. 

Another  property  of  many  normal  serums  is  Agglutinins. 
that  which  causes-  agglutination  or  clumping  of 
bacteria,  as  one  sees  it  in  the  Gruber-Widal  test 
for  typhoid.  Even  normal  human  serum  may  ag- 
glutinate the  typhoid  bacillus,  but  to  a  less  degree 
than  that  of  a  typhoid  patient. 

One  serum  often  causes  a  precipitate  in  the 
serum  of  another  animal,  or  in  a  bacterial  culture 
filtrate. 

In  considering  these  facts,  one  becomes  con- 
scious of  the  great  complexity  of  that  substance 
which  plays  so  important  a  part  in  immunity  and 
its  studv — i.  e.,  the  blood  serum. 


Precipitins. 


CHAPTER  Aa. 


Immunity 


ACQUIRED    IMMUNITY. 

Immunity  which  is  acquired  as  the  result  of 
infection  is  said  to  have  been  acquired  natm-all)', 
a  very  different  thing  from  natural  immunity. 
Immunity  which  is  acquired  artificially  may  be 
active,  as  in  vaccination;  or  passive,  as  when 
diphtheria  antitoxin  is  injected  prophylactically. 
Active  One  who  has  recovered  from  scarlet  fever,  small- 
pox, plague,  typhoid  fe'ver,  etc.,  becomes  possessed 
of  lasting  protection  against  subsequent  attacks.  On 
the  other  hand,  the  immunity  afforded  by  an  at- 
tack of  certain  other  diseases  usually  is  of  shorter 
duration:  cholera,  diphtheria,  pneumonia,  etc.  So 
far  as  known,  the  acquired  protection  is  very  spe- 
cific in  character:  e.  g.,  a  person  who  has  had 
measles  may  still  have  scarlet  fever;  or  an  attack 
of  cholera  does  not  protect  against  a  later  attack  of 
typhoid. 

In  a  number  of  diseases  one  attack  confers  no 
evident  protection  against  a  second;  gonorrhea, 
influenza,  recurrent  fever  and  malaria.  Some  dis- 
eases may  create  a  predisposition  for  recurrence: 
erysipelas,  influenza,  diphtheria  in  some  instances, 
although  a  natural  susceptibility  of  the  individual 
may  explain  repeated  attacks. 

A  very  important  factor  for  progress  in  artifi- 
cial immunity  was  the  knowledge  that  evem  a  light 
attack  of  an  infection  (scarlet  fever,  cholera, 
typhoid,  smallpox)  may  be  efficient  in  conferring 
immunity.  Such  light  attacks  are  frequently 
noted  sporadically  and  in  epidemics,  while  occa- 
sionally an  epidemic  is  mild  in  character  through- 


VACCINATION.  57 

out.  An  epidemic  of  benign  smallpox  recently 
prevailed  in  the  middle  Western  states  and  the  • 
mild  character  of  the  plague  which  was  endemic 
in  San  Francisco  will  be  remembered.  In  these 
instances  it  seems  probable  that  the  mild  charac- 
ter of  the  disease  depends  on  the  low  viriilence  of 
the  organism  which  causes  the  epidemic ;  and  the 
condition  suggests  the  possibility  of  artifLcial  at- 
tenuation of  virulent  micro-organisms  for  the  pur- 
pose of  inducing  at  will  infections  of  a  benign 
character. 

It  might  be  possible  to'  so  modify  the  virus  that  vaccination. 
protection  could  be  established  vsdthout  setting  in 
motion  the  actual  disease  even  in  a  mild  form. 
An  attenuation  of  this  nature  had  long  been  prac- 
ticed with  smallpox  virus.  Before  cowpox  was 
resorted  to  as  a  source  of  vaccine,  it  had  been  the 
custom  to  inoculate  the  genuine  virus  of  smallpox, 
for  the  purpose  of  producing  immunity.  Con- 
trary to  the  natural  expectation,  this  method, 
instead  of  reproducing  severe  smallpox,  often 
caused  the  modified  disease  which  we  call 
varioloid.  This  phenomenon  may  depend  on  the 
fact  that  the  virus  finds  the  skin  and  subcutaneous 
tissue  an  unfavorable  medium  for  the  development 
of  virulence;  a  condition  which  would  be  equiva- 
lent to  an  attenuation  of  the  microbe.  The  patho- 
genicity of  the  cholera  vibrio  in  animal  experi- 
ments is  affected  similarly  in  subcutaneous  injec-  Attenuation. 
tions.  It  is  now  generally  considered  that  cowpox 
is  smallpox  which  has  suffered  a  decrease  in  viru- 
lence because  of  its  passage  through  the  cow. 
Consequently,  when  this  weakened  virus  is  planted 
in  the  skin  of  man,  where  it  may  undergo  further 
attenuation  and  produce  the  mildest  possible  form 
of  modified  smallpox,  we  have  an  ideal  vaccine. 


58  INFECTION  AND  IMMUNITY. 

Passage.  In  a  similar  manner  the  virulence  of  tlie  anthrax 
bacillus  for  sheep  may  be  lessened  b}^  passing  the 
organism  through  the  dove.  This  metliod  of  de- 
creasing, or  in  some  cases  of  increasing,  the  viru- 
lence of  a  micro-organism  is  known  as  passage. 

No  single  method  of  attenuation  is  suitable 
for  all  organisms.  Pasteur  found  tliat  cultures 
of  the  bacillus  of  chicken-cholera  become  so  weak- 
ened when  exposed  to  the  action  of  light  and  air 
that  the}'  may  safely  be  used  as  vaccine;  also  that 
the  anthrax  bacillus  when  grown  at  42°  C.  is  at- 
tenuated and  does  not  form  spores,  and  conse- 
quently becomes  a  suitable  vaccine  for  sheep  and 
cattle.  Of  no  less  interest  to  us  is  Pasteur's 
method  of  attenuating  the  virus  of  hydrophobia 
by  desiccating  the  spinal  cords  of  infected  ani- 
mals (ral)bits)  ;  the  altered  cords  are  then  suitable 
for  the  immunization  of  individuals  who  have 
been  bitten  by  a  rabid  animal. 

Work  of  the  past  decade  has  sho'mi  that  suc- 
cessful vaccination  is  possible  against  cholera, 
tj'phoid  and  plague  by  the  inoculation  of  avirn- 
lent  cultures,  or  those  which  have  been  killed  out- 
right by  heat.  In  so  far  as  we  know  the  immunity 
Avliich  is  caused  by  vaccination  or  protective  in- 
oculation is  antibacterial,  or,  better,  antimicrobic. 
If  the  canse  of  the  disease  is  unrecognized,  as  in 
smallpox  and  hydrophobia,  there  is  no  means  of 
determining  whether  it  is  antibacterial  or  anti- 
toxic. 

Nature  of       One  may  ask  if  acquired  immunity  to  bacteria 
immunit^v.   and  to  toxins  is  due  to  the  presence  of  the  anti- 
bacterial   and    antitoxic    substances    which    were 
mentioned  in  connection  with  natural  immunity. 
Although  normal  serum  is  strongly  bactericidal 


LEUCOCYTES.  59 

for  the  typhoid  bacillus,  the  serum  of  one  who  has 
recovered  from  typhoid  fever  possesses  this  power 
to  a  much  greater  degree.  As  this  is  true  in  many 
other  bacterial  infections,  the  new  resistance  is 
held  to  depend  on  the  increase  of  bactericidal  sub- 
stances in  the  serum.  Similarly  in  acquired  im- 
munity to  diphtheria  and  to  tetanus,  the  most 
conspicuous  change  is  a  great  increase  in  the  cor- 
responding antitoxins.  The  result  is  the  same, 
regardless  of  whether  the  immunity  be  produced 
by  a  natural  attack  of  the  disease,  or  by  artificial 
immunization  with  the  specific  microbe  or  toxin. 
Accordingly  it  seems  probable  that  acquired  im- 
munity in  these  instances  depends  on  the  presence 
in  the  sertim  of  an  increased  amount  of  properties 
which,  to  a  certain  degree,  may  be  present  nor- 
mally. 

It  was  stated  in  the  section  on  natural  immun-   The  Leucocytes 
ity  that  the  leucocytes,  acting  as  phagocytes  and   immunity. 
as  resorptive  cells,  seem  to  be.  responsible,  at  least 
in  part,  for  natural  resistance  to  an  infection. 

Metchnikoff  and  his  followers  have  provided  us 
with  many  observations  wliich  are  interpreted  as 
showing  that  the  importance  of  these  cells  is  con- 
tinued into  acquired  immunity.  These  investiga- 
tors state  that  in  acquired  immunity  the  phago- 
cytes have  a  much  greater  capacity  for  ingesting 
and  killing  bacteria  and  for  absorbing  and  de- 
stroying toxins  than  when  the  animal  is  in  a  state 
of  greater  susceptibility.  It  is  also  concluded  that 
the  serum  in  active  immunity  owes  its  new  or 
more  powerful  antibacterial,  antitoxic  and  other 
properties  to  the  leucocytes,  w^hich  under  the  in- 
fluence of  the  infection  have  overproduced  and  ex- 
creted these  substances  into  the  plasma. 


CO 


rXFECTIOX  AND  IMMUNITY. 


Passive 
immunity. 


The  Leucocytes 
in  Passive 
Immunity. 


It  will  appear  later  that  recovery  from  certain 
infections  (streptococcus,  staphylococcus,  pneumo- 
coccus,  etc.)  is  not  characterized  by  tlie  formation 
of  antibacterial  or  antitoxic  substances.  In  these 
instances  it  seems  probable  tliat  the  temporary 
immnnit}',  of  which  recovery  is  the  outward  mani- 
fest-ation,  is  due  to  destruction  oi  the  bacteria  by 
phagocytic  cells.  This  conception  seems  all  the 
more  plausible  when  we  remember  the  hyperleu- 
cocA'tosis  which  characterizes  these  infections. 

Inasmuch  as  it  has  proved  possible  by  tlie  pro- 
longed immunization  of  animals  with  bacteria  or 
toxins  to  induce  a  high  concentration  of  antibac- 
terial or  antitoxic  substances  in  their  sennn,  it 
was  the  natural  expectation  that  if  such  serums 
were  injected  into  other  animals  the  latter  would 
thereby  be  endowed  with  an  increased  resistance 
to  the  infectious  agent  against  which  the  serum 
had  special  activities  (passive  immunization). 
This  has  been-  found  to  be  the  case  with  many 
antibacterial  (typhoid,  cholera,  plague,  dysentery, 
etc.)  and  some  antitoxic  serums  (diphtheria,  teta- 
nus). Unfortunately  the  protection  afforded  by 
the  injection  of  an  immune  serum  is  of  short  dura- 
tion (from  two  to  several  weeks)  ;  it  is  as  if  a  for- 
eign substance  had  been  injected,  the  fate  of  which 
is  to  be  eliminated  rapidly.  This  is  in  contrast 
to  the  condition  in  active  immunity  in  which  the 
protective  substances  are  often  formed  over  a  long 
period  by  the  body  cells. 

The  school  of  Metchnikoff  brings  the  leucocytes 
into  relation  with  passive  as  well  as  active  im- 
munity. It  is  held  that  the  immune  serum  which 
is  injected  is  potent,  because  it  stimulates  the  leu- 
cocytes to  a  greater  phagocytic  activity  in  the  case 


Opsonins. 


BACTERIOLYTIC  ENZYMES.  61 

of  antibacterial  iramiinity,  or  to  a  greater  absorp- 
tion and  destruction  of  toxins  in  the  case  of  anti- 
toxic immunity. 

Our  knowledge  of  poisons  (see  Chapter  XIV) 
is  as  yet  so  limited  that  positive  statements  can  not 
be  made  as  to  the  part  they  play  in  acquired  im- 
munity, although  it  is  thought  that  immunization 
with  some  microbes  causes  an  increase  in  the 
quantity  of  opsonins. 

Mention  may  be  made  here  of  the  well-known 
but  curious  phenomenon  that  resistance  may  vary 
with  the  age  of  the  individual.  Typhoid  fever  at- 
tacks the  adolescent  or  middle-aged  rather  than 
the  very  young  or  very  old.  Active  tuberculosis 
grows  less  common  in  the  later  decades  of  life. 
Then  we  have  what  are  distinctively  the  diseases 
of  childhood:  after  15  years  of  age  diphtheria,  for 
example,  is  uncommon.  Some  of  these  instances 
of  acquired  immunity  may  be  referable  to  differ- 
ences in  the  character  of  the  cell  receptors  at  dif- 
ferent ages,  while  perhaps  others  are  due  to  a  slow 
immunizing  process  occasioned  by  the  prolonged 
presence  of  non-pathogenic  amounts  of  the  proper 
micro-organisms. 

Emmerich  and  Loew  found  that  many  bacteria  Barterioiytrc 
produce  in  culture  media,  as  well  as  in  the  animal 
body,  substances  which  apparently  act  as  ferments 
and  which  are  able  to  kill  not  only  the  bacterium 
which  secretes  the  ferment,  but  many  others.  For 
example,  pyocyanase,  the  bacteriol3i;ic  enz3'nie  of 
Bacillus  pyocyaneus,  dissolves  pyocyaneus, 
anthrax,  diphtheria  and  typhoid  bacilli,  the  vibrio 
of  cholera,  the  streptococcus  and  staphylococcus. 
These  enzymes  usually  are  not  toxic,  and  it  is  sup- 
posed that  during  the  course  of  an  infection  they 


Enzymes. 


Immiine 
Cytotoxins. 


Immune 
Agglutinins. 


02  INFECTION  AND  IMMUNITY. 

reach  such  a  concentration  in  the  blood  that  they 
destroy  the  bacteria  which  produced  them,  thus 
bringing  about  recovery.  It  is  claimed  also  that 
they,  either  during  infection  or  as  a  result  of  re- 
peated injection  of  the  ferment,  enter  into  a  some- 
what permanent  combination  with  the  albumin  of 
the  body,  forming  the  so-called  "immune-pro- 
teidin,''  on  which  acquired  immunity  depends. 

It  is  -also  stated  that  with  "pyocyanase-immuno- 
proteidin^^  it  is  possible  to  so  immunize  a  rabbit 
that  a  subsequent  (12  days)  otherwise  fatal  dose 
of  the  anthrax  bacillus  is  harmless. 

Although  the  effects  of  these  "enzymes"  on 
anthrax  and  on  some  other  organisms  have  been 
confirmed  by  a  number  of  investigators,  their  im- 
portance in  acquired  immunity  and  in  the  recov- 
ery from  infections  is  very  doubtful.  There  is  the 
special  objection  to  this  theory  tliat  it  puts  im- 
munity on  a  non-specific  basis;  i.  e.,  pyocj'anase 
will  protect  against  anthrax,  diphtheria,  etc.. 
while,  in  reality,  all  our  clinical  and  experimental 
data  point  to  the  high  specificity  of  acquired 
immunity. 

The  serum  acquires  antibodies  not  only  for  bac- 
teria and  toxins,  but  also  for  many  other  cells  and 
sulDstances  which  may  be  used  for  immunization. 
There  are  many  immune  c}ix)toxins,  such  as  the 
serum  hemolysins,  leucotoxins,  neurotoxins, 
nephrotoxins,  etc.,  which  are  formed  as  the  result 
of  immunization  with  the  corresponding  cells. 
(See  Chapter  XIII.) 

By  systematically  injecting  an  animal  with  a 
bacterium  or  with  any  tissue  cell,  agglutinating 
substances  (the  agglutinins)  are  formed  and  may 
be  demonstrated  in  the  serum.     Like  other  anti- 


I'liEClPITl'NH. 


03 


bodies,  they  are  highly  specific  for  tlie  cell  used  in 
the  immuiiization.     (See  Chapters  IX  and  X.) 

It  has  been  found  that  toxins,  other  than  those 
of  bacterial  origin,  will  yield  antitoxins  by  im- 
munization. Such  toxins  are  snake  venom,  yield- 
ing antivenin;  ricin,  a  hemagglutinating  toxin 
from  the  castor  oil  bean,  yielding  antiricin,  etc. 


Eecentlv  what  is  termed  the  biologic  test  for   '"""?".« 

o  Precipitins 

This  test  may  a"**  „.  ,    . 

•^     The  Biologic 
Test  for 


species  has  assumed  prominence, 
be  illustrated :  A  goat  is  injected  repeatedly  with 
the  serum  of  man.  .  After  a  number  of  injections 
a  very  minute  amount  of  this  goat's  serum  will 
cause  a  precipitate  when  mixed  with  human 
serum,  but  not  when  mixed  with  the  serum  of  any 
other  animal  (except,  perhaps,  that  of  anthropoid 
apes).  The  test  is  so  delicate  that  when  a  small 
amount  of  old  dried  human  blood  is  dissolved  in 
salt  solution  and  treated  with  the  goat  serum  the 
precipitation  will  still  occur,  and  in  view  of  this 
fact,  the  test  has  become  of  medicolegal  impor- 
tance. The  wide  distribution  of  this  phenomenon 
among  all  kinds  of  animals  gives  it  great  biologic 
significance. 

Kraus  found  that  by  immunization  with  cer- 
tain bacterial  filtrates  substances  are  formed  in 
the  serum  which  cause  precipitates  in  the  filtrates. 
It  is  further  interesting  that  other  albumin-con- 
taining substances,  as  egg  albumin  or  milk,  will 
on  immunization,  yield  specific  antibodies.  The 
serum  of  an  animal  which  has  been  immunized 
with  goat's  milk  will  cause  a  precipitate  in  the 
latter,  but  not  in  coat's  milk.  (See  Chapter 
XL) 

It  has  also  been  possible  toi  obtain  specific  anti- 
bodies for  ferments :  for  the  peptonizing  ferments 


Species. 


Antiferments. 


G4  IXFECTIOy  AND  IMMUNITY. 

of  bacteria,  for  emiilsin,  lab,  fibrin  ferments,  etc. 
There  are,  however,  very  many  substances  for 
which  serum  antibodies  can  not  be  obtained;  this 
is  true  for  all  substances  of  knoAvn  chemical  com- 
position, as  acids,  bases,  salts,  and  for  the  alka- 
loids (strychnin,  morphin,  aconite,  etc.) 


CHAPTER  VII. 


TOXINS  AND  ANTITOXINS. 

Through  Ehrlich  the  word  toxin  has  come  to   thriich's 
have  a  special  significance,  being  applied  only  to  a   of  Toxin. 
certain  type  of  toxic  substances.     Toxins  have  the 
following  properties  (Ehrlich)  : 

1.  They  are  extremely  labile  substances  which 
occur  as  secretion  products  of  vegetable  or  of  ani- 
mal organisms. 

2.  Their  chemical  nature  is  uuinown.  The  im- 
possibility of  obtaining  them  in  pure  form  and 
their  great  lability  render  them  insusceptible  to 
ordinary  chemical  analysis. 

3.  An  analysis  of  a  toxin  may  be  reached  at 
present  only  through  the  medium  of  animal  ex- 
periments. 

4.  Immunization  with  toxins  yields  antitoxins. 
It  has  not  been  possible  to  obtain  antitoxins  for 
inorganic  poisons,  glucosids  and  alkaloids 
(morpliin,  strychnin,  etc.) 

5.  In  contrast  to  well-defined  chemical  poisons, 
the  action  of  toxins  is  characterized  by  a  latent  or 
incubation  period.  That  is,  following  the  introduc- 
tion of  a  toxin,  a  certain  period  of  time  elapses 
before  toxic  symptoms  appear,  and  this  period  is 
greater  than  the  time  logically  required  for  the 
absorption  of  the  toxin  through  the  circulation.'^ 

The  incubation  period  may  be  shortened  experi- 

1.  Recent  work  indicates  that  the  long  incubation  period 
of  tetanus  may  depend,  at  least  in  part,  upon  the  length 
of  time  required  for  the  toxin  to  reach  the  ganglion  cells 
through   the   axis   cylinders   of   the   motor   nerves. 


Preparation 
of  Toxins. 


GG  INFECTION  AND  IMMUNITY. 

nientallv  by  tlic  inject iou  of  large  quantities  of 
toxin,  but  it  can  not  be  eliniinatcd  ontirel_v.  Snake 
poison  appears  to  act  without  incubation  period, 
but  it  is  still  to  be  classed  with  the  toxins,  because 
of  its  power  to  cause  the  formation  of  an  anti- 
toxin. 

().  "The  facts  make  it  necessary  to  assume,  as  a 
condition  for  the  poisonous  action  of  toxins,  a  spe- 
cific chemical  union  of  the  toxin  with  the  proto- 
plasm of  the  cells  in  certain  organs."  .  .  .  "The 
affinity  of  other  poisons,  as  the  alkaloids,  for 
tissues,  depends  not  on  chemical  union,  but  on 
some  such  process  as  solid  solution  or  loose  salt 
formation.'^ 

The  preparation  of  soluble  toxins  is  relatively 
simple.  It  is  necessary  only  to  inoculate  a  suitable 
fluid  culture  medium  with  a  culture  of  the  micro- 
organism, to  allow  growth  to  take  place  for  some 
days  at  body  temperature,  then  to  pass  the  fluid 
through  a  porcelain  or  some  equivalent  filter.  The 
soluble  toxins  usually  may  be  precipitated  from 
the  filtrate  by  some  precipitant,  as  ammonium 
sulphate,  and  preserved  in  a  dried  state  for  a  long 
period.  Such  a  |)recipitate  does  not  represent  the 
toxin  in  a  pure  form,  but  various  proteid  sub- 
stances of  the  culture  medium,  as  well. 

The  bacilli  of  diphtheria  and  tetanus  Bacillus 
pyocyaneus,  and  Bacillus  hotulismus,  are  the  princi" 
pal  micro-organisms  which  produce  soluble  toxins. 

When  the  toxins  of  these  organisms  are  injected 
into  a  suitable  animal,  phenomena  similar  to  those 
produced  by  an  infection  with  the  organisms 
themselves  are  produced.  They  are  in  a  particu- 
lar sense  specific  toxins.  Some  micro-organisms, 
however,  produce  more  than  one  toxin.     The  teta- 


MULTIPLICITY  OF  TOXINS.  07 

nus  bacillus,  for  example,  secretes,  in  addition  to 
the  toxin  causing  the  nervous  symptoms  of  tetanus, 
another  (tetanolysin,  or  tetanus  hemolysin)  which 
has  the  power  to  destroy  red  blood  cells.  Ehrlich 
holds  that  the  diphtheria  bacillus  produces  not 
only  the  toxin  which  causes  the  acute  intoxication 
of  diphtheria,  but  another  of  long  incubation 
period  which  may  cause  paralysis.  Cobra  poison 
has  at  least  two  toxins,  one  which  attacks  the  nerv- 
ous tissues^ — a  neurotoxin — and'anotlier  which  at- 
tacks the  erythrocytes ;  the  two  may  be  separated 
by  appropriate  measures.  As  previously  stated, 
the  serum  of  the  eel  has  a  strong  neurotoxin  and 
a  hemotoxin. 

Some  micro-organisms  produce  one  or  more  Secondary 
soluble  toxic  substances,  Avhich  it  is  often  difficult 
or  impossible  to  consider  as  the  actual  disease- 
producing  elements  of  these  organisms.  Concern- 
ing a  disease  which  is  so  well  characterized  clini- 
cally as  tetanus,  it  is  not  difficult  to  determine 
by  inoculation  experiment  whether  one  has  in  hand 
the  specific  toxin.  The  proof  is  naturally  much 
more  difficult  in  relation  to  streptococci  and 
staphylococci,  for  example,  where  the  group  of 
symptoms  and  the  pathologic  conditions  are  not 
entirely  unique  for  the  infection.  We  are  by  no 
means  certain  that  the  hemolysin  or  the  leucoci- 
din  (toxin  for  leucocytes)  of  the  staphylococcus, 
or  the  hemolysin  of  the  streptococcus  are  the  para- 
mount disease-producing  toxins  of  these  organisms, 
although  these  substances  are  true  toxins. 

An  important  test  for  the  pathogenic  signifi- 
cance of  a  toxin  lies  in  its  ability  or  inability  to 
cause  the  formation  of  an  antitoxin  which  is 
•efficient  in  the  treatment  of  an  infection  by  the 


GS 


IXFECTIOX  A\D  IMAIUXITY 


Intracellular 

Toxins,  or 

Endotoxins. 


The  McFadyen 
Method. 


corresponding  organism.  This  is  not  the  ea.'^e 
with  the  ioxins  jufit  mentioned.  However,  one 
should  not  place  too  much  importance  on  such  a 
test,  for  it  is  quite  possible  that  we  are  not  able  on 
artificial  culture  media  to  obtain  the  toxiti  in 
such  concentration  that  the  production  of  an  effi- 
cient antitoxin  is  possible. 

There  is  a  large  class  of  organisms  the  members 
of  which  apparently  do  not  produce  soluble  toxins ; 
such  organisms,  however,  cause  highly  toxic  diseases 
(e.  g.,  t}'phoid,  cholera,  plague).  The  dead  or 
ground-up  bodies  of  such  bacteria  are  very  toxic; 
also  when  the  germs  disintegrate  by  a  process  of 
autolysis  or  self-digestion  the  culture  medium  be- 
comes toxic  because  of  the  cell  contents  which  are 
set  free.  Such  organisms  are  said  to  contain  in- 
tracellular toxins  or  endotoxins.  In  infections  by 
them  it  is  supposed  that  toxic  symptoms  are  pro- 
duced when  a  pathogenic  amount  of  the  intracel- 
lular toxins  is  liberated  by  the  bacteriolytic  action 
of  the  body  fluids  or  cells  (phagocytes). 

Nothing  is  known  of  the  nature  of  such  toxins. 
They  certainly  are  very  different  from  the  soluble 
toxins  of  diphtheria  and  tetanus,  since  immuniza- 
tion with  them  has  not  as  yet  resulted  in  the  pro- 
duction of  efficient  antitoxins.  In  spite  of  this 
fact,  however,  it  is  none  the  less  probable  that 
they  are  the  disease-producing  constituents  of  the 
organisms.  Buchner  gave  tlie  name  of  "plasmin" 
to  the  cell  juice  wliich  he  was  able  to  express  from 
some  micro-organisms. 

McFadyen,  by  grinding  large  masses  of  typhoid 
bacilli  which  had  been  rendered  brittle  by  the  tem- 
perature of  liquid  air,  obtains  from  this  organism 
a  toxic  cell  juice.     The  efficiency  of  the  antitoxin 


PREPARATION  OF  ANTITOXIN,^.  69 

wliich  he  is  said  to  obtain  by  immiimzation  with 
this  material  has  not  been  demonstrated  practi- 
cally'. It  seems  improbable  that  immimization 
with  this  "toxin"  will  yield  a  serum  differing  in 
propertiQs  from  that  obtained  by  immimization 
with  the  living  organisms. 

Toxic  substances  obtained  from  bacteria  by  the  Accidental 

•  a     •  ^        Toxic  Sub- 

action  of  strong  chemicals  and  extracting  fluids,  stances. 
may  not  represent  the  essential  toxic  substance  of 
the    organism,    but   perhaps    some    clisintegration 
product  which  iiappens  to  be  toxic. 

It  is,  of  course,  common  knowledge  that  an  anti- 
toxin is  the  blood  serum  of  an  animal,  after  the 
latter  has  been  rendered  highly  immune  by  re- 
peated injections  of  the  corresponding  toxin.  The 
horse  is  chosen  for  immunization  because  of  its 
marked  ability  to  yield  antitoxins  (diphtheria, 
tetanus),  because  of  its  size,  withstanding  much 
loss  of  blood,  and  because  of  the  readiness  with 
which  it  submits  to  manipulation. 

Manufacturing  plants  which  produce  antitoxins  Preparation 
and  other  antiserums  on  a  large  scale  have  splen- 
didly equipped  stables,  which  are  kept  in  the 
maximum  hygienic  condition,  and  from  which  rats 
in  particular  are  rigorously  excluded.-  The  horses 
are  carefully  groomed  and  fed  and  given  such  ex- 
ercise as  will  keep  them  in  a  healthy  condition. 

The  toxins,  in  solution,  are  injected  subcutane- 

2.  The  importance  of  this  is  very  great  if,  for  example, 
horses  are  receiviDg  injections  of  some  virulent  living 
niicro-organism  (as  the  plague  bacillus).  In  this  case 
living  micro-organisms  reach  the  general  circulation,  and  a 
rat  having  bitten  the  animal  could  well  contract  the 
plague  and  be  an  evident  source  of  danger,  not  only  to 
other  animals,  but  to  the  community  at  large.  Even  fly- 
proof   stalls   are   properly    instituted    in   such    cases. 


Attenuation 


70  INFECTION  AXD  IMMUNITY. 

ousi}'.^  Grave  and  even  fatal  reactions  ma}^  follow 
the  first  injections;,  if  the  toxin  has  been  given  in 
too  large  closes  or  in  too  concentrated  solutions. 
This  is  especially  true  when  injecting  tetanus 
toxin.  It  is  of  great  importance  first  to  establish 
what  the  Germans  call  a  '^Grundimmunitdt" 
which  means  a  primary  immmiity  in  the  animal 
itself  so  that  the  immunization  may  then  be 
pushed  vigorously  until  the  blood  contains  anti- 
toxin in  high"  concentration.  For  tliis  purpose  it 
]]as  been  found  necessary  to  weaken  tlie  first  tox- 
ins injected.  This  may  be  done  by  heating  the 
'of'ToTins!  toxin  solution  to  65  or  70  C.  for  an  hour;  by  add- 
ing to  it  from  0.05  to  0.4  pei-  cent;  of  the  trichlo- 
rid  of  iodin;  or  by  adding  a  solution  of  laotassiura 
iodid  in  which  iodin  has  been  dissolved  (Lugol's 
solution).  High  dilutions  of  the  unaltered  toxin 
may  also  be  used.  Gradually  the  virulence  and 
amount  of  the  toxin  injected  may  be  increased 
until  finally  the  full  virulent  toixin  is  given  in 
large  doses.  The  increase  in  dosage  must  be  very 
gradual.  Eventually  as  much  as  a  liter  or  more 
of  diphtheria  toxin  is  tolerated. 

Following  each  injection  a  reaction  occurs. 
With  diphtheria  the  local  swelling  may  be  great, 
and  sloughing  may  occur.  Following  an  injection 
of  tetanus  toxin,  tetanic  symptoms  may  appear. 
In  either  case,  there  is  some  loss  of  weight  and 
often  fever,  and  another  injection  must  not  be 
given  until  the  original  weight  is  regained  and 
the  general  behavior  of  the  animal  indicates  that 
its  former  healthy  condition  is  re-established. 

Several  months  of  such  treatment  are  necessary 

3.  For   the   production   of  antivenln   the  snake   venom   Is 
best  injeoted  intravenously. 


PRESERVATIVES.  71 

for  the  production  of  diplithoria  antitoxin  in  liigii 
concentration.  At  the  end  of  this  time  blood  is 
drawn  from  the  jugular  vein  by  means  of  a  large 
trochar  to  which  a  rubber  tube  i,s  attached.  The 
tube  leads  to  a  tall  glass  cylinder  holding  from 
one  to  two  liters,  and  into  this  the  blood  is  allowed 
to  How.  Six  liters  may  be  drawn  safely  from  a 
horse  of  average  size.*  The  most  rigid  asepsis  is 
observed  in  taking  the  blood.  The  glass  cylinders, 
appropriately  covered  to  prevent  contamination, 
are  then  set  in  a  cool,  dark  place,  and  after  the 
serum  has  separated  from  the  clot  samples  are 
taken  to  be  tested  for  their  antitoxic  value. 

The  serum,  in  bulk  or  after  being  bottled  for  orsmlms.^^* 
the  trade,  is  preserved  at  a  low  temperature  and 
in  the  dark,  0.5  per  cent,  of  carbolic  acid  having 
been  added  to  insure  sterility.  The  addition  of 
the  acid  may  cause  harmless  cloudiness  in  the 
serum,  but  does  not  destroy  the  antitoxin.  Serums 
may  be  preserved  perfectly  in  a  dried  or  frozen 
state. 

Many  facts  of  scientific  and  practical  impor- 
tance have  been  brought  to  light  through  the  im- 
munization of  animals  on  a  large  scale.  It  has 
been  found,  for  example,  that  following  each  in- 
jection of  toxin  the  amount  of  antitoxin  in  the 
blood  suffers  a  reduction,  and  only  equals  or  rises 
above  the  previous  amount  eight  or  ten  days  later. 
This  decrease  is  explained  by  assuming  that  the 
toxin  has,  to  a  certain  extent,  united  chemically 
with  the  circulating  a.nti toxin.     It  indicates  also 


4.  Some  horses  may  be  bled  as  many  as  forty  times 
without  suffering  a  conspicuous  deterioration  in  health. 
In  time,  however,  an  animal  becomes  less  valuable  as  an 
antitoxin  producer. 


72  IXFECTIOX  AXD  IMMVXITY. 

the  period  at  which  the  liorse  should  be  bled  in 
order  that  the  greatest  amount  of  antitoxin  may 
be  obtained.  It  might  even  be  dangerous  to  draw 
the  blood  before  this  time  had  elapsed,  since  some 
free  toxin  might  still  be  in  the  circulation. 

It  is  noteworthy  that  all  horses  are  not  equally 
good  producers  of  antitoxin.  One  may  yield  a 
serum  of  three  times  the  value  of  another,  al- 
though the  two  have  been  treated  identically  and 
seem  to  be  equally  immune  to  the  toxin. 

Another  most  interesting  fact  is  that,  although 
the  blood  of  an  animal  may  be  very  rich  in  anti- 
toxin, he  still  may  have  a  disproportionate  sus- 
ceptibility to  fresh  injections  of  the  toxin. 

Many  of  these  phenomena  have  not  been  ex- 
plained satisfactorily. 
standardiza-       The  nccessity  of  standardizing    antitoxins    so 
and  Antitoxins,  that  dosagc  may  be  controlled  accurately  is  self- 
evident.     To  meet  tMs  need  the  antitoxic  unit 
familiar  in  practice  was  devised. 

Behring,  and  also  Ehrlich,  decided  arbitrarily 
to  consider  as  the  antitoxic  unit  that  quantity  of  a 
serum  which  would  protect  a  guinea-pig  from  100 
fatal  doses  of  the  toxin.  Ehrlich's  original  method 
of  testing  a  serum  was  to  mix  difEerent  quantities 
with  10  fatal  doses  of  the  toxin  and  inject  each 
mixture  into  a  guinea-pig  of  250  to  300  grams' 
weight.  That- quantity  of  the  serum  which  pro- 
tected the  animal  against  the  ten  fatal  doses  of 
toxin  contained  1/10  of  an  immimity  unit,  and 
from  this  result  the  number  of  units  in  a  cubic 
centimeter  could  be  calculated.  This  method  in- 
volved the  use  of  toxin  as  the  standard  by  which 
the  value  of  the  antitoxin  was  measured,  and  it 
was  found  to  be  unreliable.     A  toxin  degenerates 


ANTITOXIC   UNIT.  73 

rather  rapidly,  retaining-  at  the  same  time  its 
binding  power  for  the  antitoxin;  hence  two  tests 
made  with  the  same  serum  two  months  apart 
•might  indicate  different  antitoxic  values  for  the 
serum.  Also  10  fatal  doses  of  one  toxin  often  re- 
quired more  antitoxin  for  neutralization  than  the 
same  quantity  of  a  second  toxin.  These  phenomena 
are  due  to  the  formation  of  toxids.  (See  next 
chapter. ) 

On  accoumt  of  these  sources  of  error,  Ehrlich 
devised  a  new  method  in  which  a  standard  anti- 
toxin or  test-seram  is  used  as  the  starting  point 
for  the  valuation  of  a  new  serum.    The  test-serum  standard 

T       I  •  1     I        (•        T-i  Antrtoxiits. 

used  at  the  Eoyal  Prussian  Institute  tor  Experi- 
mental Therapy  at  Frankfurt,  of  which  Ehrlich 
is  the  chief,  is  a  dried  and  powdered  serum  of 
such  strength  that  1  gram  contains  1,700  immun- 
ity imits;  i.  e.,  1/1700  of  a  c.c.  would  protect  a 
guinea-pig  against  100  fatal  doses  of  a  diphtheria 
toxin.^  Any  other  high-grade  serum  would  have 
answered  equally  well. 

The  institute  keeps  in  stock  a  large  number  of 

5.  In  Germany  the  various  sei'ums  are  prepared  by  pri- 
vate individuals  or  corporations  and  manufacturers  are  re- 
quired to  send  a  sample  of  every  lot  of  serum  intended  for 
the  trade  to  the  Frankfurt  Institute  that  its  exact  value  may 
bo  determined.  Each  bottle  eventually  receives  a  stamp  sig- 
nifying the  value  in  antitoxin  units  of  the  contained  serum. 
Moreover,  samples  of  every  lot  of  serum  are  retained  in  the 
in&titute,  and  from  time  to  time  these  are  tested ;  and  when 
it  is  found  that  the  samples  have  degenerated  beyond  a  cer- 
tain value  the  order  is  sent  out  to  call  in  all  serum  belong- 
ing to  the  degenerated  lot.  When  a  manufacturer  thinks 
the  serum  of  one  of  his  horses  has  a  high  value  he  may 
draw  a  small  amount  of  blood  from  the  animal  and  send 
the  serum  to  Frankfurt  for  a  preliminary  test.  If  the 
serum  is  sufficiently  strong  he  may  then  bleed  the  horse 
freely ;  if  it  is  weak  he  will  be  advised  to  continue  th? 
immunization    for    a    time. 


74  IXFECTlOy  AND  IMMUNITY. 

viaJs,  each  containing  two  grams  of  this  dried 
serum.  The  air  and  moisture  are  exhausted  from 
each  vial  and  the  latter  is  then  sealed  in  the  flaine. 
Once  in  three  months  one  of  these  vials  is  broken 
open  carefully  and  the  serum  dissolved  in  200  c.c. 
of  a  solution  made  up  of  equal  parts  of  glycerin 
and  10  per  cent,  salt  solution;  hence  each  cubic 
centimeter  of  the  solution  contains  17  units.  Dur- 
ing the  succeeding  three  months  this  antitoxic 
solution  is  used  in  the  comparative  valuation  of 
new  antitoxins;  the  solution  retains  its  strength 
unaltered  for  this  period.  For  individual  tests 
the  serum-solution  just  described  is  again  diluted 
seventeenfold,  so  that  each  cubic  centimeter  con- 
tains one  unit.  This  adds  to  convenience  and  ac- 
curacy. 

The  first  .step  in  the  process  is  to  standardize 
some  diphtheria  toxin  in  which  the  degenejative 
changes  (toxoid  formation)  have  come  to  a  stand- 
still. This  is  done  by  adding  so  much  of  the  toxin 
to  1  unit  (1  c.c.)  of  the  test  serum  that  an  excess 
of  one  fatal  dose  of  the  toxin  remains  unbound  ])y 
the  antitoxin. 

The  quantity  of  the  toxin  which  gives  this  re- 
sult is  called  the  L+dose.^  The  LO  dose  of  the 
toxin  also  is  determined,  this  being  tlie  amount 
which  is  exactly  neutralized  by  the  imit  of  anti- 
toxin. The  use  of  the  two  doses  serves  to  eliminate, 
subjective  errors  on  the  part  of  the  observer.  The 
L-f-  and  LO  doses  of  toxin  are  then  used  to  de- 
termine the  value  of  new  antitoxins.  That  quan- 
tity of  the  new  serum  which,  when  mixed  with  the 
L-f-   dose  of  toxin,  causes  the  animal   to  die   in 

6.  Ij=T.imps  (Limit)  ;  +  is  commonly  used  to  indicate 
a  fatal  rosTilt. 


NATIONAL  REOULATIONH.  75 

four  to  six  dayS;,  contains  1  .unit  of  antitoxin.  If, 
for  example,  1/100  c.c.  accomplishes  this  result, 
the  serum  is  of  one  hundredfold  strength  i.  e.,  1 
c.c.  would  contain  100  antitoxic  units. 

For  therapeutic  purposes,  it  is  desirable  to  have 
a  serum  of  high  value  in  order  to  avoid  giving  too 
large  quantities.  Several  diphtheria  serums  are 
on  the  market  Avhich  have  a  value  of  500  units  to 
the  cubic  centimeter.  It  is  difficult  to  immunize 
above  this'  point. 

In  addition  to"  the  need  of  knowing  the  exact   Pur'ty  of 

'-'  Serum. 

antitoxic  value  of  a  serum,  it  should  be  determined 
positively  that  there  is  no  contamination  of  the 
serum,  and  especially  that  no  adventitious  toxin 
(tetanus)  is  present. 

The  sterility  of  the  serum  is  determined  by  both 
a.erobic  and  anaerobic  cultures,  and  itsi  freedom 
from  toxins  by  Injecting  considerable  quantities 
into  animals.  The  serum  should  not  have  more 
than  0.5  per  cent,  of  carbolic  acid  as  a  preserva- 
tive. A  convenient  method  of  determining  this 
point  is  the  injection  of  0.5  c.c.  of  the  serum  into 
a  white  mouse.  If  more  than  this  quantity  of  the 
acid  is  present  the  mouse  dies. 

Similar  principles  prevail  in  the  standardiza- 
tion of  tetanus  antitoxin,  the  mouse  being  used  as 
tlie  test  animal.  Unfortunately  tetanus  antitox- 
ins practically  go  without  standardization  in  this 
country.  This  would  seem  to  be  for  commercial 
reasons  only,  for  they  may  be  standardized  with  a 
low  percentage  of  error. 

That  the  United  States  government  is  attempt- 
ing to  guard  the  quality  of  diphtheria  antitoxins 


76  IXFECTIOX  AXD  IMMVXITY. 

on  sale  in  our  markets  is  apparent  from  the  fol- 
lowing statement :' 

••EX\MIXATION    OF    SERUMS    MADE    BY    LICENSED 
MANUFAOTUKERS. 

"Tho  fict  of  Congress,  approved  July  1,  1902,  entitled 
'An  net  to  regulate  the  sale  of  viruses,  serums,  toxins  and 
analogous  products  in  the  District  of  Columbia,  to  regulate 
interstate  commerce  in  said  articles,  and  for  other  pur- 
poses," and  the  regulations  framed  thereunder,  approved 
Feb.  21,  1003,  imposed  upon  the  director  of  the  Hygienic 
Laboratory  the  duty  of  examining  vaccines  and  antitoxins 
for  purity  and  potency. 

"Accordingly  purchases  are  made  for  the  Hygienic  Lab- 
oratory from  time  to  time  on  the  open  market  by  officers 
of  the  Public  Health  and  Marine-Hospital  Service  stationed 
in  various  parts  oC  the  country.  The  antitoxin  is  always 
))onght  from  reliable  druggists,  who  keep  the  product  under 
pi'oper  condilions  of  liglit.  temperature,  etc.  Several  grades 
of  diphtheria  antitoxin  made  by  each  licensed  manufac- 
turer are  bought  and  sent  to  the  Hygienic  Laboratory  by 
mail  for  the  purposes  of  these  tests. 

"The  serums  are  tested  not  only  for  potency,  but  also  to 
determine  their  freedom  from  contamination  by  foreign 
bacteria,  and  finally  to  insure  the  absence  of  chemical  poi- 
sons, especially  tetanus  toxin.  Note  is  made  of  the  phys- 
ical appearance  of  the  serum,  and  tests  are  made  to  de- 
termine whether  an  excessive  amount  of  preservative  has 
been   added. 

"A  careful  memorandum  is  made  of  the  facts  given  by 
the  manufacturer,  as  stated  on  the  label,  as  to  the  num- 
ber of  units  contained  in  the  package,  and  the  date  beyond 
which  the  contents  can  not  be  expected  beyond  a  reasonable 
doubt  to  yield  a  specific  result.  Note  is  also  made  of  the 
manufacturer's  compliance  with  the  law  requiring  that  the 
product  be  plainly  marked  with  the  name  of  the  article, 
and  the  name,  address  and  license  number  of  the  manu- 
facturer. 

"Delinquencies  that  occasionally  come  to  light  in  these 
examinations  are  at  once  reported  to  the  Surgeon  General, 
U.    S.    Public    -Health    and    Mariue-Hospital    Service,    who 

7.  Taken  verbatim  from  Rosenau.  "The  Immunity  Unit 
for  Standardizing  Diphtheria  Antitoxin,"  Bulletin  No.  21  of 
the  Hygienic  Laboratory  of  the  Public  Health  and  Marine 
Hospital  Service  of  the  United  States.  M.  J.  Rosenau  is 
Director  of  the  Hygienic  Laboratory. 


OFFICINAL  ANTITOXIN.  77 

takes  the  necessary  stops  reciuiring  the  immofliate  with- 
drawal of  the  particular  lot  of  serum  from  the  market  and 
institutes  measures  to  prevent  a  repetition  of  similar  errors." 

•'SEIRUM    ANTIDIPIITHERICUM    IN    THE    I'lIARMA- 
COPEIA. 

•'The  next  edition  of  the  United  States  Pharmacopeia, 
being  the  eighth  decennial  revision,  1900,  which  is  to  ap- 
pear shortly,  will  contain  an  antitoxic  serum  for  the  first 
time.  The  serum  will  be  known  officially  as  antidiphtheric 
serum  or  Serum  anticliphthericvm,  and  the  unit  will  be 
recognized  as  that  approved  or  established  by  the  United 
States  Public   Health  and  Marine-Hospital    Service. 

"The    ofHcial    text,    which    has    been    kindly    furnished    by 
Professor   Remington    in   advance,   will   be   as    follows : 
"SERUM   ANTIDIPHTHERICUM. 

ANTIDIPHTHERIC    SERUM.       DIPHTHERIA    ANTITOXIN. 

"A  fluid  separated  from  the  coagulated  blood  of  a  horse 
Etjuus  cahaUiis,  Linue,  immunized  through  the  inoculation 
of  a  diphtheric  toxin.  It  should  be  kept  in  sealed  glass 
containers,  in  a  dark  place,  at  temperatures  between  4.5° 
and    15°    C.    (40°    and    59°    F.). 

"A  yellowish  ,or  yellowish-brown,  transparent  or 
slightly  turbid  liquid,  odorless  or  having  a  slight  odor, 
due  to  the  presence  of  the  antiseptic  used  as  a  pre- 
servative. 

"Specific  gravity:  1.025  to  1,040  at  25°  C.    (77°   P.). 

"Antidiphtheric  serum  gradually  loses  its  power,  the 
loss  in  one  year  varying  between  10  per  cent,  and  30 
per  cent.  Each  container  should  be  furnished  with  a 
label  or  statement,  giving  the  strength  of  the  anti- 
diphtheritic  serum,  expressed  in  antitoxic  units,  the 
name  and  percentage  by  volume  of  the  antiseptic  used 
for  the  preservation  of  the  liquid  (if  such  be  used), 
the  date  when  the  antidiphtheric  serum  was  last  tested, 
and  the  date  beyond  which  it  will  not  have  the  strength 
indicated  on  the  label  or  statement. 

"The  standard  of  strength,  expressed  in  units  of  anti- 
toxic power,  should  be  that  approved  or  established  by 
the  United  States  Public  Health  and  Marine-Hospital 
Service. 

"Average  dose  :   3',000  units. 

"Immunizing   dose   for   well    persons :    500   units." 


CHAPTEE  VIII. 


Biologic 
Analysis 


Neutralization 

of  Toxin  by 

Antitoxin. 


THE       STRUCTURE       OF    TOXINS     AND     ANTITOXINS 
AND    THE    NATURE    OF    THE    TOXIN-ANTI- 
TOXIN   REACTION. 

Because  of  tJie  impossibility  of  obtaining  bac- 
terial toxins  in  pnre  form,  no  conception  can  be 
gained  of  their  composition  in  terms  of  atoms  or 
molecules,  although  it  is  convenient  to  assume 
that  they  have  some  imknown  molecular  sti'uc- 
ture.  Inferences  as  to  their  nature  and  structure 
can  be  gained  only  by  means  of  the  biologic  ex- 
periment, i.  e.,  their  effects  on  animals  and  animal 
cells  under  arbitrax}^  conditions. 

Wlien  a  toxin  and  its  antitoxin  are  mixed  in 
suitable  proportions,  '  the  mixture  becomes  non- 
toxic as  the  result  of  chemical  union  of  the  two 
substances ;  each  molecule  of  toxin  has  combined 
with  a  molecule  of  antitoxin  to  form  a  new  non- 
toxic molecule  which  may  l)e  spoken  of  as  the 
toxin-antitoxin  molecule.  It  was  at  one  time  sup- 
posed that  antitoxin  had  the  power  of  destroying 
the  toxin,  perbaps  by  a  ferment-like  action.  In 
two  instances  it  has  been  possible  to  show  that 
this  is  not  the  case.  Ordinarily  toxins  are  more 
susceptible  to  heat  than  antitoxins,  but  in  the  case 
of  pyocyaneus  toxin  and  snake  venom  the  anti- 
toxins are  the  more  susceptible.  Wasserman 
found  that  when  a  neutral  mixture  of  pyocyaneus 
toxin  and  its  antitoxin  was  heated  to  a  certain 
temperature  tJie  mixture  again  became  toxic,  and 
Calmette  made  a  similar  observation  concerning 
venom  and  antivenin.     If  the  toxin  had  been  de- 


TOXIN-ANTITOXIN  REACTION.  7!J 

stroyed  b}^  the  antitoxin  the  solution  certainly 
would  not  have  regained  its  original  toxicity  on 
the  application  of  heat. 

The  following  facts  add  support  to  the  view  Chemical 
that  neutralization  consis.ts  of  chemical  union  be-  Reaction. 
tween  the  two  substancas : 

First,  neutralization  takes  place  according  to 
the  law  of  multiple  proportions,  i.e.,  ten  times  a 
given  amount  of  antitoxin  will  neutralize  a  pro- 
portionate amount  of  toxin;  second,  neutralization 
is  more  rapid  at  warm  than  at  cold  temperatures; 
and,  third,  more  rapid  in  concentrated  than  in  di- 
lute solutions.  These  are  some  well-known  laws  of 
chemical  reactions. 

"Emil  Fischer  has  shown  that  in  the  ferments,  ferments. 
definite  atom-groups  of  special  configuration  are 
present  which  above  all  else  are  requisite  for  the 
whole  phenomenon  (of  fermentation).  Only  such 
substances  as  possess  a  group  to  which  the  ferment 
group  corresponds,  as  lock  to  key,  are  subject  to 
the  action  of  a  particular  ferment."  This  applies 
to  the  action  of  a  particular  ferment  on  only  one 
kind  of  substance. 

Having  this  conception  in  mind,  Ehrlich  as-  Haptophores 
sumes  that  union  occurs  between  toxin  and  anti- 
toxin through  a  special  group  of  atoms  which  the 
toxin  molecule  possesses,  and  which  fits  into,  or 
corresponds  specifically  to,  another  group  of  atoms 
in  the  antitoxin  molecule.  These  are  spoken  of 
as  the  binding  or  haptophorons  groups  (hapto- 
phores) of  the  molecules.  The  haptophorons 
group  of  the  toxin  molecule  is  highly  specific  since 
a  toxin  can  be  neutralized  only  by  its  own  anti- 
toxin, and  naturally  the  haptophotrons  group  of 
the  antitoxin  molecule  must  be  equally  specific. 


so  INFECTION  AX  D  I  MM  U  XI TY. 

Toxophore.  The  toxiii  iiioleciile  contains  not  only  a  hapto- 
pliorus  group,  through  which  it  unites  with  anti- 
toxin in  one  instance  or  with  tissue  cells  in  the 
production  of  disease,  but  also  certain  constituents 
in  which  the  specific  activity  of  the  substance  re- 
sides. Toxin  is  able  to  work  a  change  in  tissue  cells 
after  it  has  combined  with  them.  The  toxic  prop- 
erty is  said  to  reside  in  a  toxophorous  group.  The 
toxophorous  and  haptophorous  groups  are  parts  of 
the  toxin  molecule. 
Toxoids.  It  is  a  peculiarity  of  toxins  that  they  lose  a  cer- 
tain amount  of  their  toxicity  in  the  course  of  time, 
although  their  binding  power  for  antitoxin  remains 
practically  unchanged.  In  the  language  of  the 
terms  which  were  used  above,  the  toxophorous 
groups  may  degenerate  or  disappear  and  leave  the 
haptophorous  groups  intact.  Toxins  which  have 
undergone  this  change  are  called  toxoids. 

Further  evidence  of  the  existence  of  toxoids  lies 
in  the  fact  that  when  used  for  immunization  they 
cause  the  formation  of  antitoxins.  This  is  possi- 
ble only  when  the  substance  is  able  to  unite  with 
the  tissue  cells;  therefore,  the  non-toxic  toxin  or 
toxoid  has  retained  its  haptophorous  groups. 

A  toxin  entirely  free  from  toxoids  has  never 
been  observed,  since  even  during  the  few  days  re- 
quired  for  its  preparation   a  certain  amount   of 
degeneration  occurs. 
Partial        Additional   information  concerning  the  nature 

Method  of  of  toxiu  has  been  gained  by  experimenting  witli 
mixtures  of  toxin  and  antitoxin,  in  which  the  two 
are  present  in  var\'ing  proportions.  This  is  the 
"partial  saturation"  method  of  Ehrlich.  Through 
a  vast  number  of  experiments  Ehrlich  obtained  in- 


The  Toxirf 


''TOXIN  SPECTRUM."  81 

formation  which  permitted  liJm  to  estimate  that 
300  "binding  nnits"  are  represented  in  that 
amount  of  diphtheria  toxin  (hypothetically  pure) 
which  is  exactly  neutralized  by  one  antitoxin  unit. 
If  the  entire  amoimt  of  antitoxin,  i.  e.,  200/200, 
is  added  to  the  quantity  of  toxin  in  question,  com- 
plete neutralization  of  the  latter,  of  course,  occurs. 
In  case  the  toxin  is  entirely  pure,  199/200  of  the 
antitoxin  unit  would  destroy  all  but  1/200  of  the 
initial  toxicity;  and  150/200,  or  100/200,  or 
75/200,  etc.,  of  the  antitoxin  when  added  would 
permit  corresponding  degrees  of  toxicity  tO'  be 
demonstrated  through  animal  inoculations.  It 
was  found,  however,  that  neutralization  did  not 
take  place  according  to  this  simple  scale.  The  re-  siJecirumV 
suits  were  complicated,  and  Ehrlich  has  found  it 
convenient  to  express  them  graphically  in  the  form 
of  a  "toxin  spectrum'^  (Figs.  1,  2,  3  and  4).  For 
example,  let  199/200  of  the  antitoxin  unit  be 
added  to  the  proper  amount  of  the  toxin,  198/200 
to  another  similar  amount,  197/200  to  another, 
etc., -down  to  150/200.  In  the  last  mixture,  50 
out  of  the  200  binding  units  which  the  toxin  pos- 
sesses are  free,  and  these  50,  rather  than  some  Epitoxoids. 
other  50,  are  free  because  they  have  less  aiEnity 
for  the  antitoxin  than  the  150  units  which  were 
bound.  It  has  been  foimd  that  those  units  which 
first  become  free  have  a  low  degree  of  toxicity.  It 
was  thought  that  they  might  have  lost  their  toxo- 
phorous  groups,  i.  e.,  that  they  were  toxoids;  and 
because  of  their  weak  affinity  for  antitoxin  they 
were  called  epitoxoids.  It  was  found,  however,  that 
they  possessed  a  rather  constant  though  low  degree 
of  toxicity  and  that  the  toxic  action  was  characteris- 


82 


INFECTIOX  AX  J)  IMMLMTY. 


tic.  Injection  was  followed  b)'  some  local  edema, 
Toxon.  ^^^^^  ^y  ^  ^^^S  incubation  period,  and  finally  by 
cachexia  and  paralysis.  On  account  of  this  char- 
a.ctcristic  toxic  action  and  the  long  incubation 
period,  Ehrlich  has  concluded  that  the  so-called 
epitoxoid  is  in  reality  a  second  toxin  which  is  se- 
creted by  the  diphtheria  bacillus.  This  he  now 
designates  as  toxon^  in  order  to  distinguish  it  from 
that  other  constituent  of  diphtheria  bouillon,  the 
toxin,  which  causes  the  acute  phenomena  of  diph- 
theria. 
Protoxoids.  Lot  ouc  uow  add  still  sniallor  amounts  of  the 
antitoxin  unit  to  the  200  binding  units  of  the 
toxin.  When  149/200  are  added  it  is  found  that 
a  certain  amount  of  true  toxin  remains  free,  the 
quantity  which  is  unbound  being  in  direct  propor- 
tion to  the  amount  of  antitoxin  withheld.  Conse- 
quently when  but  50/200  antitoxin  unit  is  added 
the  amount  of  free  toxin  corresponds  to  100  bind- 


1.  The  existence  or  non-existence  of  toxons  has  created 
a  great  deal  of  discussion  among  investigators.  The  Swed- 
isli  chemist,  Arrheniiis,  lias  recently  attempted  to  apply 
oen.ain  principles  of  physical  chemistry  to  the  study  of 
toxins  and  antitoxins.  It  is  a  v/ell-known  fact  that  some 
chemical  substances,  when  in  solution,  have  the  power  of 
breaking  up  into  their  constituent  parts:  thus  sodium 
clilorid  breaks  np  in  part  into  sodium  and  chlorin,  as  so- 
dium or  chlorin  Ions  or  electrolytes.  The  dissociated  so- 
dium or  chloi-in  may  then  enter  into  combination  with  any 
other  suitable  substances  which  may  be  present.  Arrhenlus 
holds  that  this  is  the  case  with  the  toxin-antitoxin  molecule, 
that  it  may  to  a  certain  extent  again  break  up  into  sep- 
arate toxin  and  antitoxin.  He  believes  that  this  dissociated 
toxin  is  the  substance  which  Ehrlich  has  been  calling 
toxon.  Madsen.  who  formerly  had  done  much  work  with 
toxons,  has  now  joined  with  Arrhenius  in  support  of  the 
dissociation  theory.  In  spite  of  the  reasonableness  of  this 
theory,  Ehrlich  and  his  followers  continue  to  uphold  the 
toxon  as  an  independent  toxic  substance,  and  have  pub- 
lished   additional    experiments   to    support    their   position. 


J'JiOTOTOXINS,  ETC. 


83 


Jng  units.  If  true  toxin  only  remained  it  could 
then  be  said  that  the  constitution  of  this  toxin  is : 
toxin  150  and  toxon  50.  However,  it  may  be 
found  that  as  49/200,  48/200,  etc.,  to  0/200  anti- 
toxin unit  are  added,  no  increase  of  free  toxin  is 
found,  although  the  antitoxin  added  has  been 
bound.  In  this  case,  the  50  binding  units  of  toxin 
which  have  the  greatest  affinity  for  antitoxin  are 
non-toxic;  i.  e.,  they  are  toxoids,  and  since  they 
have  the  maximum  affinity  for  antitoxin  they  are 
called  protoxoids.     . 

It  has  been  assumed  also  that  a    toxoid    may   Syntoxoids. 
exist  which  has  an  aihnity  for  antitoxin  exactly 
equaling  that  which  toxin  possesses;  this,  as  yet 
purely  hypothetical  constituent,  bears  the  name  of 
syntoxoid. 

Figure  1  is  a  grapliic  representation  of  the 
toxin  just  described  (Madsen).  Probably  no  two 
toxins  have  the  same  constitution.  The  toxon 
zone,  for  example,  could  well  be  much  larger  in 
one  diphtheria  toxin  than  in  another. 

Eefinements  in  experimentation  show  that  even   Proto-, 

^  Deutero-  and 

the  true  toxin  is  not  uniform  in  its  virulence  and  Tritotoxins. 
its  affinity  for  antitoxin.  Accordingly  a  proto- 
toxin,  a  deuterotoxin  and  a  tritotoxin  may  be  rec- 
ognized by  this  same  partial  saturation  method. 
(See  Fig.  2.)  For  example,  it  may  be  found  that 
when  a  portion  of  the  antitoxin  unit,  between  the 
limits  of  149/200  and  125/200.  is  withheld,  a 
toxin  is  left  free  which  is  less  virulent  than  that  re- 
maining free  between  the  limits  of  124/200  and 
100/200 ;  and  from  this  point  on  the  new  unbound 
toxin  may  be  still  more  virulent.  The  first  would 
be  tritotoxin,  the  second  deuterotoxin  and  the 
third  prototoxin. 


84 


lyFECTIOK  AND  IMMUNITY 


VTotot{>;(o(<i 

i 

'  If'ill    II 

Toxone 

0  10    \i>    Jo    to    10    i»    n   to   f«  /«>  110  1X0  /to  /yj  /fo  Ao  /7»  /»*  /f«  l«o 

Fiiiuro    1. 


i 

i 

m 

w//i'M 

i 

'm 

7~o  >f  o  n  e 

^ 

toxt-n  , 

Figure    2. 

^  JJfutero-      yz-ti-         ■  t 


ioxcn>  p 

Figure    3. 


TratatoxoiJ  g^eutfrp  JTritotoxoidj   a 


oxone 


2huTerQ-     TritoToxin      |9 
Tox(  n  ■_■  p 


Figure  4. 
Figures  1,  2,  3  and  4  are  taken  from  Aschoff's  "Bhr- 
llch's  Seitenkettentheorie.  etc.,"  Ztschr.  f.  Allgem.  Physiol., 
vol.  i,  1902.  Figure  1  is  a  toxin  spectrum  worked  out  by 
Madsen.  Figures  2,  3  and  4  are  spectra  representing  the 
changes  in  qualitative  and  quantitative  structure  which  a 
toxin  may  undergo  with  age,  as  described  in  preceding  para- 
graphs. 


ORIGIN  OF  ANTITOXIN.  85 

The  "spectrum"  of  a  toxin  changes  with  its  age. 
The  prototoxin,  and  portions  of  the  deutero-  or 
tritotoxin  maj^  disappear  because  of  toxoid  forma- 
tion. Such  changes  have  led  to  the  recognition  of 
an  alpha  and  a  beta  modification  of  the  toxin. 
The  alpha  modifications  of  all  three  toxins  readily 
become  toxoids.  Only  the  beta  modification  of  the 
deuterotoxin  remains  constant.  The  toxon  also 
remains  relatively  intact  (Figs.  2,  3  and  4). 

This  very  complicated  method  of  investigation 
was  also  undertakeai  by  Madsen  in  the  study  of 
tetanus  toxin,  for  which  a  somewhat  similar 
"spectrum"  was  constructed. 

Such  spectra  have  not  been  worked  out  in  de- 
tail for  some  of  the  vegetable  toxins,  as  ricin  and 
abrin,  but  it  is  known  that  they  form  toxoids. 

Snake  venom  differs  from  the  bacterial  toxins 
in  structure  (See  Part  II,  Chapter  III). 

The  idea  was  originally  advanced  that  antitoxin  The  Formation 
was  transformed  toxin,  a  change  in  the  latter  hav- 
ing been  effected  through  some  action  of  the 
tissues.  In  that  case,  the  amount  of  antitoxin  pro- 
duced should  be  roughly  equivalent  to  the  amount 
of  toxin  injected.  This,  however,  was  found  not 
to  be  the  case.  A  single  injection  of  tetanus  toxin 
may  yield  100,000  times  the  amount  of  antitoxin 
necessary  to  neutralize  the  toxin  injected.  An  in- 
teresting experiment  is  on  record  which  shows  the 
fallacy  of  the  view  just  mentioned.  An  animal, 
the  serum  of  which  was  rich  in'  antitoxins,  was 
bled  repeatedly  until  an  amount  of  blood  which 
equaled  the  total  quantit;\^  normalh^  present  in  the 
animal's  body  was  drawn.  Yet  the  antitoxic 
power  of  the  new  formed  blood  was  practically  un- 
changed. 


8{j 


IXFECTIOy  AND  IMMUNITY. 


Ehrlich's 

"Side-Chain" 

Theory. 


Receptors. 


Multiplicity 
of  Receptors. 


Met-chnikoff,  to  explain  this  "overproduction" 
of  antitoxin,  has  suggested  that  the  toxin  molecules 
may  be  taken  up  b}'  phagocytic  cells  and  broken  up 
into  an  indefinite  number  of  smaller  molecules, 
each  of  which  then  is  altered  in  some  obscure  man- 
ner so  as  to  constitute  a  molecule  of  antitoxin. 

The  views  of  Ehrlich  have  found  wide  accept- 
ance, and  have  provided  a  valuable  working  h)-- 
potliesis  for  many  investigations.  A  considera- 
tion of  this  subject  introduces  one  at  once  to  the 
well-known  side-chain  theory  of  immunity  of 
Ehrlich.  It  may  be  considered  briefly  at  this  point, 
in  so  far  as  it  involves  the  origin  and  nature  of 
antitoxin.  Ehrlich  considers  it  fundamental,  in 
regard  to  the  metabolic  activity  of  cells,  to  assume 
that  the  cell  constituents  must  enter  into  chemical 
combination  with  food  substances  in  order  that  the 
latter  may  be  made  available  for  the  use  of  the 
cell.  It  is  supposed  that  cells  contain  cer- 
tain atom  groups  of  unknown  chemical  nature 
which  make  possible  the  binding  of  food  sub- 
stances. The  name  of  receptor  was  given  to  such 
groups,  since  substances  are  received  into  the  cell 
through  them.  Inasmuch  as  the  foods  and  some 
other  substances  which  penetrate  the  cells  differ 
in  their  chemical  nature,  it  is  probable  that  there 
are  various  receptors  for  the  various  types  of  sub- 
stances. The  binding,  however,  is  but  a  prelimi- 
nar\^  step  to  profound  changes  which  the  substance 
may  next  undergo,  through  the  action  of  other, 
more  vital,  cell  constituents.  That  is  to  say,  the 
receptor  is  but  a  link  to  bring  the  substance  into 
relationship  with  the  vital  activities  of  the  cell, 
which  Ehrlich  supposes  may  reside  in  a  hypotheti- 
cal  "Leistungsl-prn^    (action   center   or  nucleus). 


ACTION  OF  TOXINS. 


87 


In  view  of  this  conception  one  readily  un(]erstands 
the  propriety  of  considering  the  receptor  as  a  side- 
cbain  of  the  "Leistungslccrn,"  jiLst  as  the  chemist 
speaks   of  the  various   cronps  Avhich   may  be  at- 


Side-Chains. 


Fig.  5. — Graphic  representation  of  receptors  of  the  first 
order  and  of  toxin  uniting  with  the  cell  receptor,  a.  Cell 
receptor ;  6,  toxin  molecule ;  c,  haptophore  of  toxin  mole- 
cule ;  d,  toxophore  of  toxin  molecule,  e,  haptophore  of  the 
cell  receptor.  From  Ehrlich's  "Schlussbetrachtungen," 
Nothnagel's  System  of  Medicine,  vol.  viii.  This  cut  is  not 
to  be  taken  as  representing  the  actual  morphology  of  toxins 
or  cell  receptors.  Nothing  is  known  of  their  morphology, 
if,  indeed,  they  have  any.  The  cut  is  intended  merely  to 
represent,  in  a  graphic  manner,  the  supposed  chemical 
structure  and  mode  of  action  of  these  substances.  This 
statement  applies  also  to  Figures  6  and  7. 

tached  to  the  benzol  ring,  or  benzol  nucleus,  as 
side-chains  (See  Chapter  XV). 

In  preceding  pages  it  has  been  emphasized  that  Action  of 
a  toxin,  in  order  that  it  may  injure  a  cell,  must 
enter  into  chemical  combination  with  its  constitu- 


88     .  INFECTION  AND  IMMUNITY. 

ents,  and  it  is  a  fundameutal  tenet  of  the  Ehrlieh 
theory  that  this  union  is  one  which  takes  place 
between  the  toxin  and  a  cell  receptor  (side-chain). 
Tlie  cell  receptor,  then,  either  is  a  haptophore  or 
possesses  a  haptophore  as  a  part  of  its  complex. 

As  the  physiologic  demands  are  probably  re- 
sponsible for  the  character  of  the  various  recep- 
tors, it  is  not  likely  that  special  receptors  are 
created  when  some  unusual  substance,  as  a  bac- 
terial toxin,  is  introduced  into  the  body.  Conse- 
quently, when  toxin  unites  with  a  cell,  it  probably 
occupies  receptors  which,  under  normal  circum- 
stances, are  employed  in  some  physiologic  process. 

If  some  inert,  non-toxic  substance  should  com- 
bine extensively  "with  cells,  a  corresponding  num- 
ber of  receptors,  which  ordinarily  are  used  for 
normal  metabolism,  would  be  thrown  out  of  func- 
tion. Union  of  this  nature  would  be  equivalent 
to  an  injur\^  of  the  cell,  and  it  is  possible  that  the 
action  of  toxoids  is  of  this  mild  nature. 

When  toxin  unites  with  cells  there  is  involved 
not  only  the  diversion  of  cell  receptors  from  their 
customary  functions,  but  in  addition  the  destruc- 
tive action  of  the  toxin  on  the  vital  parts  of  the  cell 
(perhaps  on  the  "Leistungshern") .  The  more 
toxin  introduced,  the  greater  the  number  of  cell 
receptors  bound,  and  the  greater  the  injun^  to  the 
cell. 
Hypothesis  In  casc  a  non-fatal  amount  of  toxin  lias  been 
bound,  but  sufficient  to  cause  some  injury,  how 
does  the  cell  respond  to  the  injury?  Weigert,  a 
few  years  ago,  gave  expression  to  a  hypothesis 
which  is  held  to  have  some  bearing  on  this  ques- 
tion. In  studying  regeneration  following  injury 
he   concluded   that  tissues  have   the  tendency  to 


STRUCTURE  OF  ANTITOXIN.  89 

reproduce  not  only  to  the  extent  of  making  good 
the  injury,  but  that  an  excess  of  new  tissue  re- 
sults. The  clearest  example  of  this  occurrence  is 
that  of  scar  formation,  in  which  a  seeming  excess 
of     new     connective     tissue     cells     is     formed,  . 

which  later  disappears  in  part.  Similarly,  when  of  side-chains. 
a  non-fatal  amount  of  toxin  unites  with  the 
receptors,  a  cell  defect  or  injury  is  created.  The 
cell  has  for  practical  purposes  lost  so  many  recep- 
tors. This  loss  affects  the  vital  activities  of  the 
cell,  the  "Leistungshern"  and  new  receptors,  iden- 
tical with  those  occupied,  are  reproduced.  Follow- 
ing the  law  stated,  they  are  reproduced  in  excess 
of  the  number  injured,  and  the  excess  may  be  so 
great  that  the  cell  may  be  overfilled  with  them — 
so  overfilled  that  many  are  discharged  and  reach 
the  general  circulation.  These  cast-off  receptors, 
or  side-chains,  still  retaining  their  power  of  unit- 
ing with  toxin,  constitute  our  antitoxins.  As 
Behjnng  has  stated  it,  the  receptor,  when  attached 
to  the  cell,  is.  the  agent  through  which  the  latter 
is  attacked,  but  when  cast  off  from  the  cell  becomes 
its  protector  (Fig.  5). 

As"  regards  the  structure  of  the  antitoxin  (cast-   Receptors  of 

~,  I       \       ..     •  ,  in        the  First  Order. 

on  receptor),  it  is  necessary  to  assume  only  the 
presence  of  the  proper  haptophorous  .group.  Ehr- 
lich  designates  all  receptors  of  this  simple  type  as 
"receptors  of  the  first  order."  In  following 
sections  we  will  have  to  do  with  receptors  of  the 
second  and  third  orders. 

Wassermann   gives   the  following  list   of   anti- 
toxins: 

ANTlTOXIIs^S   FOR   BACTERIAL   TOXIXS. 

Diphthei'ia  antitoxin. 
Tetanus  antitoxin. 


90  IXFECTIOX  AXD  JMMUMTY. 

Botulism  antitoxin. 
P3'0cyanens  antitoxin. 
Symptomatic  anthrax  antitoxin. 
Antileucocidin,  an  antitoxin  for  the  leucocytic 

poison  of  the  staphylococcns. 
Antitoxins  for  the  blood  dissolvino:  toxins  of  a 

number  of  bacteria. 

ANTITOSINS   FOR  ANIMAL   TOXINS. 

Antlvenin  for  snake  poison. 
Antitoxin  for  scorpion  poison. 
Antitoxin  for  spider  poison. 
Antitoxins  for  certain  poisons  of  fish,  eel  serum, 
salamander,  turtle,  and  for  wasp  poison. 

ANTITOXINS  FOE  PLANT  TOXINS. 

Antiricin,  for  a  red  blood  corpuscle  poison  of 

the  castor  oil  bean. 
Antiabrin,  for  a  similar  poison  of  the  jequirity 

bean. 
Antirobin,  for  robin,  a  locust  tree  poison. 
Anticrotin,  for  crotin,  a  toxin  froni  the  bean  of 

Croton  iiglium,  the  croton  oil  bean. 
Hay  fever  antitoxin,  for  the  toxin  of  pollens 

\\'hich  cause  hay  fever. 

ANTTFERMENTS. 

Antirennet. 

Antipepsin. 
Antitrypsin. 
Antiiibrinferment. 

Antiurease,  for  urease,  a  urea  splitting-  ferment. 
Antilaccase. 
Antityrosinase. 
Antisteapsin. 

Antiferments  agvainst  the  ferments  of  bacterial 
cultures. 


OTHER   ANTlTOXlNf^.  91 

The  above  are  true  antitoxins.  There  are  other 
substances,  however,  which  occasionally  exert  an 
antagonistic  action  on  toxins,  although  they  prob- 
ably are  not  true  antitoxins.  For  example,  it  has 
been  found  that  cholesterin  neutralizes  the  action 
of  tetanolysiin,  the  hemolytic  toxin  of  the  tetanus 
bacillus. 

The  discovery  of  Hektoen  that  certain  salts  are 
able  to  neutralize  the  toxic  action  of  some  serums, 
by  combining  with  the  so-called  complement,  may 
also  be  mentioned  in  this  connection. 


CHAPTER  IX. 


Specificity. 


Wjdal  and 
Griinbaum. 


Normal 
Agglutinins. 


THE  PHENOMENON  OF  AGGLUTINATION. 

Agglutination,  in  the  bacteriologic  sense,  refers 
to  the  clumping  and  sedimentation  of  a  homogene- 
ous suspension  of  micro-organisms  by  the  action  of 
a  serum. 

Although  a  number  of  investigators  had  ob- 
served the  phenomenon  of  agglutination,  Gruber 
and  Durham  first  saw  its  significance.  They  found 
that  the  reaction  was  a  specific  one,  i.  e.,  that  the 
serum  which  would  cause  the  strongest  agglutina- 
tion of  a  micro-organism  was  that  of  an  animal 
which  had  been  made  immune  to  it  by  repeated 
injections. 

Widal's  service  consisted  in  the  utilization  of  the 
phenomenon  as  an  aid  in  the  diagnosis  of  typhoid 
fever.  He  is  the  originator  of  clinical  serum 
diagnosis.  It  is  perhaps  largely  a  matter  of  acci- 
dent that  we  speak  of  the  Widal  reaction  rather 
than  the  Griinbaum  reaction.  Griinbaum  was  car- 
rying on  the  same  work  at  the  same  time,  but 
Widal  preceded  him  in  the  publication  of  his  more 
extensive  work. 

In  the  chapter  on  natural  immunity  it  was 
stated  that  normal  serums  often  are  able  to  ag- 
glutinate bacteria.  ISTormal  human  serum  may  ag- 
glutinate the  typhoid,  colon,  pyocyaneus,  and  dys- 
entery bacilli,  and  occasionally  the  staphylococcus 
and  cholera  vibrio;  it  does  not  agglutinate  the 
streptococcus  and  some  other  organisms.  In  cer- 
tain cases  it  may  agglutinate  the  typhoid  bacillus 


NORMAL  AND  IMMUNE  AGQLUTININH.       93 


even  when  the  serum  is  diluted  to  one  in  thirty,  a 
point  of  practical  importance  in  the  clinical  use  of 
the  test.  When  a  normal  serum  is  found  to  liave  a 
high  agglutinating  power,  a  previous  infection  by 
the  micro-organism  is  to  be  thought  of.  This  pos- 
sibility receives  emphasis  from  the  fact  that  the 
serum  of  a  new-born  child  is  devoid  of  many  of  the 
agglutinins  which  are  found  in  later  life.  Hence, 
of  the  so-called  normal  agglutinins,  many,  after 
all,  may  be  acquired  properties. 

The  term  immune  agglutinin  is  applied  to  the 
agglutinating  substance  in  a  serum,  when  the 
property  has  developed  as  a  result  of  infection,  or 
of  systematic  immunization  with  the  organism. 
They  are  formed  during  infections  with  the  organ- 
isms of  typhoid,  cholera,  dysentery,  plague,  etc. 

For  the  artificial  production  of  agglutinins,  the 
bacteria  may  be  injected  into  the  veins,  subcutane- 
ous tissue,  or  peritoneal  cavity ;  in  some  cases  they 
may  be  fed  to  animals,  rubbed  into  the  skin,  or 
sprayed  into  tlie  lungs.  If  certain  micro-organ- 
isms are  sealed  up  in  a  collodion  sac  and  placed  in 
the  abdominal  cavity  of  an  animal,  an  agglutinat- 
ing serum  will  be  formed ;  the  necessary  substances 
diffuse  through  the  sac  and  reach  those  body  cells 
which  produce  the  agglutinin.  It  is  not  necessary 
that  living  bacteria  be  injected ;  in  fact,  the  strong- 
est agglutinin  is  said  to  be  formed  by  the  injection 
of  bacteria  which  have  been  killed  by  a  tempera- 
ture of  62  C.  In  certain  instances  agglutinins  are 
produced  by  immunization  with  disintegration 
products  of  bacteria  or  with  bacterial  extracts. 

Nearly  all  bacteria,  even  when  non-pathogenic, 
will  give  rise  to  agglutinating  serums  when  in- 
jected ;  but  not  all  have  the  power  equally.   Mcolle 


Immune 
Agglutinins. 


Agolutinin 
Producing 
Organisms. 


04  INFECTION  AND  IMMUNITY. 

and  Trenell  distinguisli  three  groups  of  bacteria 
in  regard  to  their  aggiutinability  by  the  homolo- 
gous antiserums.^  The  first  group  includes  easily 
aggiutinable  organisms,  for  the  most  pathogenic: 
Typhoid,  dysentery,  cholera,  plague,  glanders,  and 
the  colon,  psittacosis,  pyocynneus  bacilli,  and  B. 
enteritidis.  Tliey  yield  agglutinating  serums  read- 
ily either  as  a  result  of  infection  or  by  immuniza- 
tion. The  second  group  comprises  organisms 
which,  during  infection  or  convalescence,  do  not 
cause  the  formation  of  agglutinins,  but  may  be 
forced  to  do  so  by  systematically  injecting  them 
into  animals.  In  the  third  group  are  included 
those  which,  even  during  prolonged  immunization, 
rarely  cause  the  formation  of  agglutinating 
serums:  the  Friedlander  bacillus.  These  facts 
may  be  taken  as  an  index  of  the  diseases  in  which 
we  may  expect  to  obtain  the  agglutination  reaction 
by  the  serum  of  the  patient. 
Variations  in        The  degree  of  agglutinating  power  which  may 

Agglutinogenic    ,  i  ,     •        -,   ^        •  *"     .       ,  .         ^       .  ,-,  ^-r    ' 

Power  of  be  obtained  by  immunization  varies  greatly,  van 
rganisms.  ^:|^^.  Yg^(:]g  gpeaks  of  a  tjQDhoid  serum  which  in  a 
dilution  of  one  in  one  million  was  agglutinating, 
and  Durham  had  a  cholera  serum  which  was  ef- 
fective in  a  dilution  of  one  in  two  millions.  Such 
powerful  serums  are  rarely  obtained. 

Even  two  different  strains  of  the  same  organism 
may  differ  in  their  ability  to  cause  the  formation 
of  agglutinins.  It  is  generally  said  that  a  typhoid 
strain,  which  is  agglutinated  with  difficulty,  gives 
rise  to  a  weak  agglutinating  serum,  while  an  easily 

1.  The  homologous  organism  for  a  typhoid  serum,  for  ex- 
ample, is  the  typhoid  bacillus,  and  vice  versa  ;  other  organ- 
isms, or  other  serums,  are  heterologous.  These  are  commonly 
used  terms. 


DISTRIBUTION  AND  VARIATIONS.  95 

agglutinable  strain  gives  a  strong  agglutinin.  The 
logic  of  this  will  become  apparent  when  we  con- 
sider the  nature  of  the  bacterial  substance  which 
causes  the  body  to  produce  agglutinin. 

That  the  agglutinating  power  of  the  serum  of  a   variations  in 

i       1-1  ^-       1.  •         T  1  J.       1  •  £      1.     Quantity  of 

typhoid  patient  varies  irom  day  to  day  is  a  tact  Agglutinin. 
of  practical  importance.  It  may  be  thirty  times  as 
strong  one  day  as  the  next,  and  may  even  disap- 
pear entirely  for  a  day  or  two.  Hence  the  impor- 
tance of  making  more  than  one  test  in  a  suspicious 
case,  when  the  first  trial  has  been  doubtful  or 
negative.  There  is  no  adequate  explanation  for 
this  great  variation.  It  is  said  that  mixed  infec- 
tions, intestinal  hemorrhage,  or  a  sudden  pouring 
out  of  t}^hoid  bacilli  into  the  circulation  may 
cause  a  reduction  in  the  agglutinating  power.  This 
occurrence  has  an  important  bearing  on  the  possi- 
bility of  using  the  agglutinating  power  of  the 
serum  as  a  prognostic  sign.  Although  it  has  often 
been  noted  that  in  fatal  infections  agglutinins  may 
be  absent  from  the  serum,  the  variations  just  men- 
tioned indicate  that  prognosis  could  not  be  based 
safely  on  the  result  of  a  single  agglutination  test. 

The  agglutinating  substance  is  found  in  the  Distribution  of 
highest  concentration  in  the  blood  serum,  but  it  in^Bo"dy?'"' 
may  be  demonstrated  in  the  various  body  fluids 
and  in  extracts  of  the  organs ;  it  is  said  to  be  par- 
ticularly rich  in  the  milk.  It  is  present  in  the 
serum  of  an  artificially  produced  blister,  and  it  has 
been  recommended  that  blistering  be  resorted  to 
in  order  to  obtain  serum  for  the  test.  The  bile 
often  agglutinates  the  typhoid  bacillus,  but  the 
power  has  no  necessary  relationship  to  a  pre-exist- 
ing infection ;  it  is  possible  that  the  agglutination 
in   this    case  is   due  to   obscure   chemical   causes 


90 


IXFECyi'WX  AND  IMMIMTY. 


Inheritance. 


Agglutination 
and  Immunity. 


rather  than  to  the  usual  serum  agghitinin.  The 
administration  of  pilocarpin  causes  a  rise  in  the 
agghitinating  power  of  the  tears,  sputum  and  some 
other  body  fluids;  the  drug  increases  cell  secre- 
tions. 

"When  typhoid  fever  occurs  during  pregnancy, 
agglutinins  may  appear  in  the  serum  of  the  fetus. 
On  the  one  hand  it  has  been  held  that  agglutinin 
passes  from  the  mother  to  the  fetus,  or,  on  the 
other  hand,  that  the  presence  of  agglutinins  arises 
from  infection  of  the  fetus  itself. 

Although  the  milk  may  be  very  rich  in  agglu- 
tinin, it  is  doubtful  if  the  serum  of  a  breast-fed 
child  undergoes  much  increase  in  its  a2:2:lutinating 
power  because  of  the  ingestion  of  the  milk.  The 
intestinal  Juices    (trypsin)    digest  agglutinin?. 

The  origin  of  agglutinins  in  the  animal  body  is 
not  loiOT^m. 

One  of  tlie  most  interesting  and  important  phe- 
nomena in  the  study  of  immimity  is  the  so-called 
Pfeiffer  reaction.  An  animal  which  has  been 
rendered  immime  to  cholera  by  repeated  injections 
of  cholera  vibrios  has  the  power  of  digesting  or  dis- 
solving the  latter  when  they  are  placed  in  the  fresh 
serum  or  in  the  peritoneal  cavity  of  the  immunized 
animal.  Gruber  and  Durham  were  studying  this 
phenomenon  in  the  test  tube  when  they  first  ob- 
served the  agglutination  reaction.  It  was  found 
that  the  agglutinating  property,  as  well  as  the  bac- 
tericidal power,  was  the  result  of  immunization. 
Inasmuch  as  an  increase  in  the  bactericidal  power 
of  a  serum  points  to  the  existence  of  an  acquired 
immunity,  the  question  naturally  arises :  Does  the 
associated  property  of  agglutination  have  a  similar 
significance  ? 


RELATION  TO  IMMUNITY.  97 

Many  observations  indicate  that  the  two  activi- 
ties are  distinct;  that  they  depend  on  different 
substances  in  the  serum.  The  following  are  the 
important  points  involved: 

1.  The  bactericidal  power  is  destroyed  at  56  C, 
while  agglutinins  resist  a  temperature  of  62  C. 

2.  In  certain  cases  it  has  been  possible  to  cause 
the  bacteria  to  absorb  the  agglutinin  from  the 
serum,  leaving  the  bactericidal  substance  intact. 

3.  A  serum  may  be  bactericidal,  but  not  agglu- 
tinating. 

4.  During  the  course  of  natural  or  experimental 
typhoid  fever  or  cholera  the  development  of  the 
agglutinating  and  bactericidal  powers  may  not  be 
parallel.  In  cholera,  the  agglutinating  power  may 
disappear  soon,  but  the  bactericidal  power  remains 
for  a  long  time. 

5.  Micro-organisms  which  have  been  killed  by  a 
bactericidal  serum  may  lose  their  toxicity;  ag- 
glutinated bacteria  remain  virulent. 

Besredka  found  an  apparent  relationship  be- 
tween agglutination  and  immunit}^;  if  t3^phoid 
bacilli  were  agglutinated  before  they  were  injected 
into  the  abdomen  of  a  guinea-pig  the  animal  would 
recover,  but  if  they  were  not  agglutinated  death 
resulted.  The  explanation  offered  for  this  loss  of 
virulence  is  that  the  bacilli  being  agglutinated  and 
immobilized  are  more  readily  taken  up  by  the 
phagocytes;  if  phagoc^^tosis  is  inhibited  by  some 
means  the  agglutinated  organisms  are  found  to  be 
still  virulent. 

Koch  has  attempted  to  use  the  agglutination 
test  with  the  tubercle  bacillus  as  an  index  of  im- 
munity against  tuberculosis.  This  is  not  accepted 
as  a  reliable  test  for  the  immunity,  but  is  perhaps- 


98 


INFECTION  AND  IMMUNITY. 


Technic  of  the 

Agolutinatlon 

Test. 


The  Bacterial 
Suspension. 


a  general  index  of  the  ability  of  the  individual  to 
form  antibodies  for  this  organism.  This  method 
was  devised  inasmuch  as  the  bactericidal  action  of 
a  serum  on  the  tubercle  bacilhi?  is  not  readily  de- 
termined. 

One  may  use  two  methods  of  determining  the 
agglutination  of  bacteria:  1.  The  macroscopic  or 
naked  eye  observation  of  the  clumping  and  sedi- 
mentation of  a  homogeneous  suspension  of  the 
bacteria  in  test-tubes;  2,  the  microscopic  observa- 
tion of  the  clumping  of  the  organisms  when  the 
latter  are  mixed  with  serum  and  mounted  as  a 
"■hanging-drop"  preparation.^ 

^Vl'len  the  organism  to  be  tested  grows  rapidly, 
it  is  the  custom  to  use  a  young  culture,  one  which 
has  grown  on  an  agar  surface  or  in  bouillon  for 
from  eighteen  to  tAventy-four  hours.  Older  cul- 
tures of  the  typhoid  bacillus  or  of  the  cholera 
vibrio  are  agglutinated  with  more  difficulty  than  a 
young  culture.  If  an  agar  culture  is  used,  the 
bacteria  may  be  washed  from  the  surface  by  pour- 
ing five  or  ten  cubic  centimeters  of  physiologic  salt 
solution  into  the  tube  and  shaking  vigorously ;  the 
resulting  suspension  is  then  ready  for  use.  For 
either  the  macroscopic  or  microscopic  test  it  is 
absolutely  essential  to  have  a  homogeneous  suspen- 
sion of  the  bacteria,  in  order  to  avoid  misinterpre- 
tations which  may  be  occasioned  by  the  accidental 


2.  For  fi  hanging-drop  pTpparation  it  is  necessary  to  have 
a  slide  with  a  saucer-shaped  depression  on  one  surface.  -A 
drop  of  the  solution  to  be  examined  is  mounted  on  a  cover- 
glass,  and  the  latter  is  then  mounted,  drop  side  down,  over 
the  depression  and  the  edges  of  the  cover-glass  sealed  with 
vaselin  or  paraffin.  There  is  ample  room  for  motile  organ- 
Isms  to  swim  about  in  such  a  preparation,  and  the  loss  of 
"motility   incident  to  agglutination   is   readily  observed. 


TECHNIC.  99 

or  natural  clumping  of  some  of  the  organisms; 
the  tubes  should  be  shaken  thoroughly  before  the 
emulsions  are  used.  This  uniformity  of  suspen- 
sion is  readily  accomplished  with  such  organisms 
as  the  typhoid  bacillus  and  cholera  vibrio,  motile 
organisms,  but  when  they  grow  in  chains  (strep- 
tococcus) or  in  coherent  masses  (diphtheria  and 
tiibercle  bacilli)  more  violent  measures  must  be 
resorted  to.  Daily  shaking  of  a  liquid  culture  of 
the  diphtheria  or  tubercle  bacillus  is  fairly  effec- 
tive, but  the  medium  must  be  passed  through  a 
paper  filter  before  it  can  be  used  safely;  in  this 
way  the  larger  clumps  are  removed.  Some  inves- 
tigators dry  a  large  quantity  of  tubercle  bacilli, 
grind  them  up  thoroughly  in  an  agate  mortar  and 
suspend  the  particles  in  salt  solution;  the  frag- 
mented condition  of  the  organisms  does  not  inter- 
fere with  their  participation  in  the  reaction.  One 
should  have  a  uniform  technic  in  preparing  a  bac- 
terial emulsion  in  order  to  obtain  as  nearly  as  pos- 
sible the  same  number  of  bacteria  in  a  given  vol- 
ume of  solution,  on  different  occasions.  For  exam- 
ple, one  may  uniformly  suspend  a  twenty-four- 
hour  agar  culture  in  ten  cubic  centimeters  of  salt 
solution.  A  uniform  technic  makes  it  possible  to 
observe  the  quantitative  relationship  which  exists 
between  the  mass  of  bacteria  to  be  agglutinated 
and  the  agglutinating  power  of  the  serum. 

To  obtain  serum  for  the  test  one  may  resort  to  To  obtain 
blistering;  place  a  cantharides  plaster  from  one- 
half  to  three-fourths  of  an  inch  square  on  the  ab- 
dominal skin,  protect  it  with  a  dressing,  and  in 
about  twelve  hours  remove  the  serum  with  a  steril- 
ized hypodermic  syringe.  Or,  one  may  collect  in  a 
small  test  tube  .5  to  1  c.c.  of  blood  from  the  lobe 


Serum. 


100  INFECTION   AND    IMMUNITY. 

of  the  ear  or  finger-tip,  and  draw  off  the. serum 
after  it  has  separated  by  clotting.  It  is  the  cus- 
tom in  some  well-equipped  laboratories  to  fill  sev- 
eral U-shaped  capillar}^  tubes  with  blood  from  the 
lobe  of  the  ear  and  to  separate  the  blood  from  the 
serum  at  cmce  by  centrifugation.  The  custom  of 
drying  a  few  drops  of  blood  on  a  covorglass  or  on 
filter  paper,  and  of  sending  this  preparation  to  a 
laboratory  for  the  agglutination  reaction,  has  been 
practiced  quite  extensively,  and  is  a  justifiable 
procedure  when  it  is  not  possible  to  collect  the  pure 
serum.  It  has  the  disadvantage  that  the  experi- 
menter never  knows  exactly  how  much  blood  has 
been  collected,  and  consequently  can  not  perform 
the  test  with  exact  dilutions  of  the  serum,  the  im- 
portance of  which  will  be  pointed  out  l^elow.  Tlie 
red  corpuscles  and  debris  in  such  a  preparation  also 
interfere  with  the  clearness  of  the  field  in  micro- 
scopic examination,  a  difficulty  which  may  be 
partly  overcome  by  filtering  the  dissolved  serum. 
_  Serum  When  only  a  small  amount  of  serum  is  available, 
it  is  necessary  to  use  the  microscopic  method. 
Normal  human  serum,  when  concentrated,  and 
even  when  diluted  to  one  in  ten  or  higher,  some- 
times agglutinates  the  typhoid  l^acillus  and  some 
other  organisms;  the  same  serum,  when  diluted  to 
one  in  forty  or  one  in  sixty,  may  not  agglutinate. 
The  serum  of  a  typhoid  patient,  however,  or  of  a 
typhoid  convalescent  rarely  fails  to  agglutinate  in 
these  higher  dilutions.  It  is  generally  held  that 
a  dilution  of  one  in  forty  or  fifty  is  sufficiently 
high  to  eliminate  the  possibility  of  agglutination 
by  a  non-t^^hoid  serum,  and  sufficiently  low  to 
render  the  serums  of  all,  or  nearly  all,  t\'phoid  pa- 
tients agglutinating.    The  necessity  for  dilution  of 


MEASUREMENT.  101 

the  serum  is  emphasized  by  the  additional  fact 
that  infections  with  related  organisms,  as  the  colon 
bacillus,  cause  a  slight  increase  in  the  agglutinat- 
ing power  for  the  typhoid  bacillus  along  with  a 
relatively  large  increase  of  colon  agglutinins.  A 
test  with  a  low  dilution  of  this  colon  serum  might 
give  a  positive  reaction  with  the  typhoid  bacillus 
and  lead  to  an  incorrect  interpretation;  but 
if  a  dilution  of  one  in  forty  were  used,  the  non- 
agglutination  of  the  typhoid  bacillus  would  speak 
against  a  typhoid  infection.  This  will  be  consid- 
ered under  "group  agglutination'^    (Chapter  X). 

A     convenient    method     of     measuring    small   The  "Loop" 

,  .         -, ,  -,  .      ^  .  Measurement. 

amounts  of  culture  and  serum  is  by  means  of  a 
fine  platinum  wire  which  is  bent  at  its  tip  to  form 
an  eyelet  or  "loop."^  If  one  places  one  loop  of 
serum  into  a  small  watch  glass  or  hollow-ground 
slide,  and  adds  nine  loops  of  bouillon  or  of  salt 
solution,  a  dilution  of  one  in  ten  is  reached.  Five 
loops  of  this  mixture  with  five  of  the  diluent  gives 
a  dilution  of  one  in  twenty.  One  loop  of  the  sec- 
ond dilution,  to  which  is  added  one  of  the  culture 
suspension,  gives  the  desired  dilution  of  one  in 
forty.  The  last  may  be  mixed  directly  on  the 
coverglass,  and  then  inverted  on  a  hollow-ground 
slide.  It  is  readily  seen  how  with  even  a  minute 
quantity  of  serum,  one  may  make  the  test  with  di- 
lutions of  one  in  ten,  one  in  twenty,  one  in  thirty, 
one  in  forty,  etc.,  details  which  are  necessary  for 
a  correctly  performed  test.  It  is  important  that 
in  the  different  dilutions  the  same  amount  of  bac- 
terial emulsion  be  used. 

3.  PfelfEer  Introduced  a  conventional  "loop"  of  such 
dimensions  that  it  holds  2  milligrams  of  bacterial  cells  as 
they  g^re  taken  from  a  solid  surface,  like  that  of  agar. 


10-J 


INFECTION   AND   IMMUNITY 


The  Microscopic 
Reaction. 


The  Macroscop- 
ic Reaction. 


In  the  macroscopic  test,  more  serum  is  neces- 
sary, though  the  quantity  need  not  be  large,  and 
the  dilutions  are  made  in  test  tubes  of  suitable 
size.  One  should  always  deal  with  definite  quan- 
tities of  the  serum  dilutions,  and  should  always 
add  the  same  amount  of  bacterial  emulsion  in  tlie 
various  tubes  involved  in  a  test. 

If  agglutination  occurs  in  the  microscopic  prep- 
aration described  above,  one  sees,  with  the  high 
power,  in  the  course  of  from  fifteen  minutes  to  a 
lialf-hour,  that  two  or  more  micro-organisms 
whicli  come  in  contact  have  a  tendency  to  remain 
in  this  position.  In  the  case  of  a  motile  organism 
(typhoid)  the  movements  may  be  exaggerated  for 
a  time.  In  the  course  of  the  next  few  hours,  other 
cells  are  added  to  incipient  groups  and  new  groups 
originate.  Motility  becomes  less  and  less  and  event- 
ually ceases,  in  a  characteristic  reaction.  The 
maximum  change  has  taken  place  in  from  six  to 
eight  hours.  Not  less  than  four  or  five  cells  which 
are  permanently  agglutinated  are  considered  in- 
dicative of  a  positive  reaction;  the  test  is  most 
decisive  when  large  masses  are  formed,  so  large  that 
they  are  seen  readity  with  a  low  magnification.  A 
similar  preparation  to  which  no  serum  has  been 
added  should  always  be  made,  in  order  to  eliminate 
spontaneous  or  "auto-agglutination"  as  a  possible 
source  of  error. 

In  a  macroscopic  test,  the  uniform  cloudiness  of 
the  mixture  of  serum  and  hacteria  becomes 
changed  by  the  formation  of  smaller  and  larger 
flakes  or  clumps  of  bacteria,  which  in  the  course  of 
a  few  hours  sink  to  the  bottom  as  a  white  precipi- 
tate, leaving  a  clear  overlying  fluid.     Here  also  a 


UNIT  OF  A(J(1LUTININ. 


103 


control  tube,  to  wJiicli  no  scrinii  lias  been  added, 
should  be  preserved  for  comparison. 

The  body  temperature,  which  may  be  obtained 
in  a  thermostat,  facilitates  the  reaction. 

The  value  of  an  agglutinating  serum  can  not  be 
expressed  in  units  with  the  exactness  that  is  at- 
tained in  measuring  diphtheria  antitoxin  for  the 
following  reasons :  1,  The  limits  of  the  reaction  are 
not  sufficiently  definite ;  2,  a  given  mass  of  bacteria 
has  the  power  of  absorbing  varying  amounts  of 
the  agglutinating  substance,  depending  on  the  con- 
centration of  the  latter;  and  3,  it  is  impossible  to 
obtain  standard  bacterial  emulsions. 

One  may  arbitrarily  decide  on  a  unit  similar  to 
that  of  Zilpnik,  in  which  a  serum  which  is  able 
to  agglutinate  a  given  mass  of  bacteria  in  a  dilu- 
tion of  one  in  forty  is  taken  as  the  standard.  If  a 
similar  amount  of  a  serum  aggkitinates  in  a  di- 
lution of  .1  in  120  it  is  said  to  be  of  threefold 
strength. 

The  value  of  the  agglutination  reaction  as  a 
clinical  diagnostic  aid  will  be  considered  later  in 
connection  with  the  individual  diseases. 

A  consideration  of  agglutination  would  be  in- 
complete if  one  did  not  mention  the  phenomenon 
as  it  occurs  with  cells  other  than  those  of  bacteria, 
in  particular  the  red  blood  cells.  The  serums  of 
many  animals,  as  stated  in  a  previous  chapter,  are 
toxic  for  the  erythrocytes  of  some  other  species. 
In  some  instances,  the  corpuscles  lose  their  hemo- 
globin under  the  influence  of  the  serum  (hemoly- 
sis) ;  in  other  instances,  or  even  with  the  same 
serums,  the  corpuscles  are  throAvn  into  clumps  and 
settle  to  the  bottom  of  the  test  tube,  leaving  a  clear 
overlying  fluid.     The  analogy  with  the  bacterial 


The  Agglutinin 
Unit. 


Agglutination 
of  Red  Blood 
Corpuscles. 


lOi  INFECTION  AND   IMMUNITY. 

agglutinins  goes  still  further,  in  view  of  the  fact 
that  the  formation  of  these  'liemagglutinins" 
may  be  induced  artificially  in  the  body  of  an  ani- 
mal by  the  injection  of  erythrocytes  from  another 
species.  An  animal  does  not  form  agglutinins  for 
its  own  cells  (auto-agglutinins),  and  rarely,  if 
ever,  for  the  cells  of  another  member  of  the  same 
species  (iso-aggiutinins).  "Wliat  is  said  in  the 
next  chapter  concerning  the  specificity  of  the  bac- 
terial agglutinins  also  holds  for  the  hemaggluti- 
nins. 
Plant  Hemag-  Certain  plant  toxins,  true  toxins  with  hapto- 
phorous  and  toxophorous  structures,  agglutinate 
red  blood  cells:  ricin,  abrin,  crotin,  etc.  Some  of 
the  earliest  and  most  important  work  which 
Ehrlich  has  done  in  the  field  of  immunity  was  ac- 
complished with  these  plant  toxins. 


glutinins. 


CHAPTEE  X. 


THE   NATURE   OF   THE    SUBSTANCES    CONCERNED    IN 
AGGLUTINATION. 

Two  substances  are  concerned  in  agglutination :  Terms. 
one,  the  active  or  agglutinating  substance,  exists 
in  the  serum,  while  the  other,  the  substance  acted 
on  or  the  agglutinable  substance,  is  present  in  the 
bacteria.  The  agglutinable  substance  is  generally 
supposed  to  be  passive  in  the  reaction,  while  the 
agglutinating  property  seems  to  possess  a  ferment- 
like element,  which  acts  on  the  agglutinable  sub- 
stance. Agglutinin,  the  term  used  in  the  preced- 
ing chapter,  is  now  generally  applied  to  the  sub- 
stance in  the  serum.  Eecently  the  bacterial  con- 
stituent has  been  called  agglutinogen,  because  of 
the  belief  that  the  agglutinable  substance,  when 
introduced  into  the  animal  body,  stimulates  the 
latter  to  the  formation  of  agglutinin;  hence  ag- 
gutinogen  means,  not  agglutination-producing, 
but  agglutinin -producing.  These  shorter  terms 
will  be  used  for  the  sake  of  convenience. 

The  presence  of  agglutinogen  in  an  organism  AggiutiaogRn. 
may  be  demonstrated  in  three  ways :  1.  The  mere 
fact  of  its  agglutinability  by  a  serum  is  evidence 
of  the  presence  of  an  agglutinable  substance.  2. 
If  during  infection  or  immunization  the  serum  ac- 
quires agglutinating  properties,  the  bacterium  pos- 
sesses an  agglutinogenic  substance.  3.  If  a  cul- 
ture is  mixed  with  a  serum  containing  the  specific 
agglutinin,  and  after  a  period  of  contact  is  re- 
moved by  centrifugation.  the  resultant  disappear- 


lOG 


IXFECriON   AND   IMMUNITY. 


Distribution  of 
Agglutinogen. 


The  Precipita- 
tion Reaction. 


ance  of  agglutinin  from  the  scrum,  which  may  be 
demonstrated,  shows  that  something  in  the  bac- 
teria (agglutinogen)  has  combined  with  the  ag- 
glutinin. 

The  location  of  agglutinogen  in  the  bacterial 
cells  has  received  some  discussion.  There  is  a  tend- 
ency to  believe  that  it  exists  in  the  cell  envelope  or 
perhaps  on  its  surface.  It  appears  to  be  formed  in 
the  cell,  and,  in  some  cases,  it  may  be  excreted  into 
a  surrounding  medium;  certainly  when  bacteria 
die  and  disintegrate  agglutinogen  is  liberated.  The 
filtrates  of  certain  cultures  (entirely  free  from 
bacterial  cells),  when  injected  into  animals,  will 
cause  the  formation  of  agglutinins.  Also,  just  as 
a  micro-organism  is  able  to  absorb  agglutinin  from 
the  corresponding  antiserum  by  a  process  of 
chemical  union,  so  a  filtrate  of  the  type  mentioned 
is  able  to  neutralize  the  agglutinating  power  of  the 
serum.  In  these  instances  agglutinogen  becomes 
free  as  a  consequence  of  disintegration  of  some  of 
the  iDacterial  cells. 

The  filtrates  of  certain  cultures  exhibit  another 
phenomenon  when  they  are  mixed  with  their  spe- 
cific antiserums;  this  has  to  do  with  the  bacterial 
precipitins  of  Kraus.  If,  for  example,  the  filtrate 
of  an  old  typhoid  bouillon  culture  is  mixed  with 
antityphoid  serum,  a  distinct  precipitate  is  formed 
which  eventually  settles  to  the  bottom  of  the  tube. 
This  is  a  specific  reaction,  and  does  not  occur  if  the 
filtrate  is  mixed  with  some  other  immune  serum. 
It  is  thought  by  some  that  this  so-called  precipi- 
table  substance  in  the  filtrate  is  identical  with  the 
agglutinable  substance  (agglutinogen),  but  this 
point  is  still  the  subject  of  investigation. 

Agglutinogen   may   be    extracted    from    micro- 


AOaLUTlNOGEN   AND  AOULUT/NIN. 


107 


organisms  by  chemical  processes.  The  presence 
of  the  substance  in  the  extracts  becomes  manifest 
when  immunization  with  them  causes  the  forma- 
tion of  an  agglutinating  serum.  This,  again,  is 
the  "test  of  immunization." 

The  agglutinogen  of  one  bacteriiim  is  not  iden- 
tical with  that  of  any  other.  If  they  were  identi- 
cal, immunization  with  the  one  would  yield  an  ag- 
glutinating serum  of  equal  power  for  both  cells; 
this,  however,  is  not  the  result  obtained.  On  the 
other  hand,  the  agglutinins  of  two  difEerent  organ- 
isms may  coincide  to  a  certain  degree,  as  will  be 
shown  under  the  subject  of  "group  agglutination." 
Certain  experiments  gO'  to  show  that  the  agglutin- 
ogen of  even  a  single  micro-organism  is  not  uni- 
form substance.  One  portion  is  heat-susceptible, 
being  destroyed  at  63  C,  while  another  portion  is 
said  to  resist  a  temperature  of  165  C.  Such  tech- 
nical questions  continue  to  be  investigated. 

Agglutinogens  are  said  to  pass  through  semi- 
permeable membranes,  while  agglutinins  do  not. 

Smith  and  Eeagh  distinguish  two  kinds  of  ag- 
glutinogen in  those  bacteria  which  possess  fiagellge, 
one  peculiar  to  the  cell  body,  and  the  other  to  the 
flagellse. 

Agglutinin  may  be  precipitated  completely  from 
a  serum  by  the  sulphates  of  magnesium  or  ammo- 
nium, when  the  salts  are  used  in  proper  concentra- 
tions. Because  of  their  reaction  to  such  precipi- 
tating agents,  agglutinins  are  thought  to  belong  to 
the  globulin  fraction  of  serums ;  whether  globulins 
or  not,  they  are  precipitated  with  them. 

Agglutinins  resist  digestion  with  pepsin  and 
papayotin,  but  are  destroyed  after  prolonged  ex- 
posure to  the  action  of  trypsin.     An  agglutinating 


Multipficity  of 
Agglutinogens. 


Flagellar 
and  Somatic 
Agglutinogens. 


Properties  of 
Agglutinins. 


108 


IXFECTION   AND   IMMUNITY. 


Structure  of 
Agglutinogen. 


Structure  of 
Agglutinin. 


Zymotoxic 
Group. 


scrum  which  is  dried  and  kcjDt  free  from  moisture 
and  the  action  of  light  retains  its  power  unaltered. 
Similar  to  agglutinogen,  agglutinin  is  thought  not 
to  be  a  uniform  substance,  one  portion  being  sus- 
ceptible to  heat,  and  another  portion  resistant; 
these  have  been  called  alpha  and  beta  agglutinins. 

It  is  convenient  to  speak  of  the  reaction  between 
agglutinin  and  agglutinogen,  and  of  the  process  in 
the  body  through  which  agglutinins  are  formed,  in 
terms  of  the  side-chain  theory.  Accordingly,  if 
that  constituent  of  micro-organisms  which  we  have 
termed  agglutinogen  is  the  substance  which  stimu- 
lates the  tissues  to  form  agglutinin,  we  must  as- 
sign to  it  a  haptophorous  group  through  which  it 
may  unite  with  the  receptors  of  the  tissue  cells. 
This  haptophore  comes  into  play  again  in  the  union 
between  agglutinogen  and  agglutinin,  which  pre- 
cedes agglutination.  There  is  no  reason  for  as- 
signing to  agglutinogen  any  other  structure  than 
this  single  haptophore ;  it  is  a  passive  bod}^,  similar 
to  antitoxin,  and  has  no  other  function  than  that 
of  uniting  either  with  cell  or  with  agglutinin. 

Agglutinin  also  must  have  a  haptophorous  or 
binding  group,  inasmuch  as  it  enters  into  combina- 
tion with  agglutinogen.  In  addition  to  this  bind- 
ing group,  experiments  have  showm  that  agglutinin 
possesses  a  toxic  constituent,  which  is  analogous 
to  the  toxophorous  group  of  the  toxin  molecule. 
In  this  case,  however,  it  is  called  a  zymotoxic, 
zymophorous  or  agglutinophorous  group ;  suppos- 
edly it  has  a  ferment-like  activity  (Fig.  6).  The 
analogy  with  toxins  goes  further,  in  that  the 
zATuotoxic  group  of  agglutinin  may  degenerate  or 
may  be  destroyed,  leaving  the  haptophorous  group 
with  its  binding  power  for  agglutinogen  practi- 


A0GLUTIN0ID8. 


109 


cally  unaltered;  these  are  agglutiuoids,  just  as  Aggiutinoids. 
toxins  when  changed  in  a  similar  way  are  called 
toxoids.  A  serum  which  is  rich  in  agglutinin  may 
be  changed  into  one  rich  in  agglutinoid  by  expo- 
sure to  a  temperature  of  from  60  to  75  C,  and  by 
the  action  of  acids  or  alkalies;  the  change  also 
takes  place  spontaneously  in  the  course  of  time, 
when  the  agglutinin  is  in  solution. 

Agglutinoids  are  detected  by  methods  analogous 
to  those  used  in  the  recognition  of  toxoids.  If 
toxoids  unite  with  all  the  antitoxin  in  a  solution, 
there  naturally  remains  no  antitoxin  to  unite  with 
true  toxin  which  may  be  added  subsequently.  Sim- 
ilarly, if  all  the  agglutinogen  in  a  mass  of  micro- 
organisms has  united  with  inactive  agglutinoid, 
agglutinin  which  is  added  subsequently  would  have 
no  point  of  attack  and  the  reaction  of  agglutina- 
tion would  not  occur.  So  we  may  say  that  when 
bacteria  are  treated  with  a  serum  which  has  lost 
its  original  agglutinating  power,  and  the  bacteria 
are  thereby  made  insusceptible  to  the  action  of  a 
fresh  agglutinating  serum,  the  former  serum  con- 
tains agglutinoids. 

Sometimes  it  is  found  that  even  a  fresh  serum,  Proaggiu- 
when  concentrated,  will  cause  less  agglutination 
than  when  diluted.  This  has  been  referred  to  the 
presence  of  agglutinoids  which  have  a  stronger 
affinity  for  agglutinogen  than  has  the  agglutinin; 
when  of  this  character  they  are  called  proagglu- 
tinoids,  and  accordingly  are  analogous  to  the  pro- 
toxoids  mentioned  earlier.  As  the  serum  is  diluted 
the  concentration  of  the  proagglutinoids  becomes 
less,  and  at  a  time  when  they  are  so  dilute  that  they 
have  no  influence  on  the  reaction,  the  agglutinins 


110 


INFECTION    AM)    IMMUNITY. 


Two  Stages  in 
Agglutination. 


Group 
Agglutination. 


are  still  present  in  such  quantity  that 
tion  is  brought  about. 

The  presence  of  some  salt  is  necessary 


agglutina- 


for  the 


occurrence  of  agglutination.  Bordet  found  that 
if  the  salts  were  removed  from  the  serum  and  from 
the  suspension  of  bacteria  by  dialysis,  and  the  two 
were  then  mixed,  agglutination  did  not  occur;  if 
a  small  trace  of  sodium  chlorid  was  added  the  re- 
action took  place  promptly.  Furthermore,  if  the 
serum  was  completely  removed  from  the  bacteria 
by  repeatedly  washing  them  in  distilled  water,  it 
was  found  that  the  microbes  had  absorbed  the  ag- 
glutinin, but  the  latter  remained  inactive  until  the 
salt  was  added. 

This  experiment  not  only  suggests  a  haptophor- 
ous  as  distinguished  from  a  z^^motoxic  group,  but 
also  indicates  that  agglutination  consists  of  two 
phases.  The  first  phase  represents  the  union  of 
agglutinin  vrith  the  bacteria,  while  in  the  second 
are  included  the  other  changes  necessary  for  the 
clumping  of  the  organisms,  in  which  the  activity 
of  the  ZAanotoxic  group  is  represented.  The  action 
of  the  salt,  just  cited,  is  unknown. 

The  properties  of  serums  which  are  of  interest 
in  immunity  are  now  being  studied  by  chemists, 
notably  by  Arrhenius.  The  study  of  mass  action, 
of  chemical  equilibrium  between  agglutinin  and 
agglutinogen,  for  example,  and  of  the  dissociation 
of  the  compound  after  it  has  once  formed,  are 
subjects  under  investigation,  but  which  are  too 
technical  to  be  entered  on  here. 

"Group  agglutination"  has  been  referred  to.  By 
this  is  meant  the  ability  of  an  antimicrobic  serum 
to  agglutinate  certain  other  organisms  which  mor- 
phologically,  biologically   and   often   pathogeneti- 


GROUP  AGGLUTINATION.  Ill 

cally,  are  closely  related  to  the  homologous  bac- 
terium. In  these  instances,  the  agglutinating 
power  is  greatest  for  the  homologous  organism, 
and  the  degree  to  which  the  heterologous  organisms 
are  agglutinated  is,  to  some  extent,  an  index  of 
the  proximity  of  the  relationship  of  the  latter  to 
the  former.  Antityphoid  serum  has  been  found  to 
agglutinate  the  psittacosis,  colon,  paracolon,  and 
paratyphoid  bacilli  and  Bacillus  enteritidis,  but 
the  action  is  never  so  strong  as  on  the  typhoid 
bacillus  itself.  We  are  to  understand  that  this 
power  to  agglutinate  related  organisms  represents 
something  more  than  the  normal  property  of  the 
serum;  there  has  been  an  actual  increase  in  agglu- 
tinin for  the  heterologous  bacteria  as  a  result  of 
infection  or  immunization  by  the  primary  organ- 
ism. 

Having  typhoid  fever  in  mind,  this  is  a  rule 
which  works  both  ways.  Infections  with  the  colon 
bacillus  and  related  organisms,  and  sometimes 
with  organisms  not  closely  related,  as  the  staphylo- 
coccus, may  cause  an  increase  in  agglutinin  for  the 
typhoid  bacillus.  The  importance  of  this  fact  is 
evident,  and  it  may  explain  the  positive  Gruber- 
Widal  reaction  sometimes  found  in  infections 
other  than  typhoid. 

Inasmuch  as  the  highest  agglutinating  power  is  chief  Aggiutinii 
always  manifest  against  the  homologous  organism,  finins?"^^^  "' 
this  is  spoken  of  as  the  chief  agglutinin  {Haupt- 
agglutinin)  of  the  serum,  while  the  weaker  agglu- 
tinins for  other  organisms  are  called  partial  or  ad- 
ventitious agglutinins,  or  coagglutinins  {MUag- 
glutinin). 

The  phenomenon  of  group  agglutination  would   SpecifichV. 
seem  to  violate  the  specificity  which  we  are  in  the 


112  INFECTION   AND   IMMUNITY. 

habit  of  attributing  to  the  reactions  of  immunity; 
yet  a  reasonable  explanation  has  been  offered  for 
the  occurrence.  It  is  probable  that  the  proto- 
plasms of  all  cells  have  certain  constituents  in 
common,  and  that  the  closer  the  relationship  be- 
tween two  different  cells  the  greater  is  the  simi- 
larity of  their  constituents.  In  view  of  this  prob- 
ability, Durham  has  used  the  following  illustra- 
tion in  the  explanation  of  group  agglutinations : 
The  typhoid  bacillus  contains  certain  constituents, 
agglutinogenic  molecules,  which  one  may  desig- 
nate as  a,  b,  c,  d,  and  e;  these  differ  among  them- 
selves in  unlcnown  respects,  but  each  is  able  to 
stimulate  to  the  formation  of  a  corresponding  ag- 
glutinin. The  serum,  then,  would  have  the  ag- 
glutinin molecules  A,  B,  C,  D  and  E,  also  differing 
among  themselves,  but  having  at  least  one  property 
in  common — that  of  causing  agglutination  of  the 
typhoid  bacillus  by  uniting  with  the  correspond- 
ing agglutinogenic  molecules.  In  this  sense  noth- 
ing could  be  more  specific.  The  Bacillus  enteri- 
tidis,  closely  related  to  the  typhoid  organism,  may 
possess  the  agglutinogenic  molecules  c,  d,  e,  f,  g, 
and  h,  and  following  the  principle  expressed  above 
would  stimulate,  in  the  body,  to  the  formation  of 
the  agglutinin  molecules  C,  D,  E,  F,  G  and  H. 
Inasmuch  as  the  agglutinogens  c,  d  and  e  are  com- 
mon to  the  two  bacilli,  the  agglutinins  C,  D  and  E, 
which  are  present  in  both  serums,  would  affect 
either  of  the  two  organisms.  The  typhoid  serum, 
however,  would  contain  five  agglutinins  for  the 
typhoid  bacillus  and  only  three  for  the  Bacillus 
enteritidis,  consequently  the  action  would  be 
stronger  against  the  typhoid  bacillus;  mutato  mu- 
tandis, the  same  applies  to  the  enteritidis  serum. 


SEBUM    DILUTIONS. 


113 


The  same  line  of  reasoning  would  explain  the  in- 
creased agglutinating  power  of  an  anticolon  serum 
for  the  typhoid  bacillus. 

A  further  elaboration  of  this  principle  may  be 
made  in  a  case  in  which  two  different  strains  of 
the  same  organism  (typhoid  bacillus)  have  some- 
what different  agglutinogenic  molecules;  Conse- 
quently the  homologous  immune  serums  for  the 
two  organisms  might  not  coincide  in  their  ag- 
glutinating powers  for  a  third  strain  of  the  bacil- 
lus. 

In  view  of  the  points  mentioned,  it  is  clear  that  importance 
specificity  of  a  given  serum  may  be  determined  Dilutions. 
only  by  diluting  the  serum  to  such  an  extent  that 
the  coagglutinins  practically  are  eliminated,  the 
chief  agglutinin  being  present  in  so  much  greater 
concentration  that  it  is  still  able  to  agglutinate 
the  homologous  bacterium. 

Theoretically,  it  is  also  important  for  the  spe- 
cificity of  the  reaction  that  the  particular  strain 
of  the  organism  to  be  used  for  the  test  correspond 
in  its  agglutinogenic  molecules  or  receptors  with 
those  of  the  strain  used  for  the  immunization ;  the 
agglutinogenic  receptors  should  be  typical  for  the 
organism. 

It  is  doubtful  if  group  agglutination  occurs 
among  all  closely  related  bacteria,  inasmuch  as 
Kolle  found  that  it  did  not  exist  among  the  vib- 
rios. 

It  is  thought  possible  that  the  multiple  agglu- 
tinating power  of  a  serum  may  be  caused  by  mixed 
infections  in  some  instances.  Although  this  is  to 
be  kept  in  mind,  one  should  not  overestimate  its 
diagnostic  importance,  because  a  similar  multi- 


Mixed 

Infections. 


114  rXFECTIOX    AXD    IMMUXITY. 

plicity  ma}'  result  I'rom  infection  l)v  a  single  micro- 
organism. 
Production  of       Thc  explanation  of  the  production  of  aggluti- 
^^''"thrlkh   "ii^s  by  the  body,  according  to  the  conception  of 
Theory.   Eijpiich,  Is  similar  to  that  already  given  for  the 
production  of  antitoxins.     That  is  to  say,  the  ag- 
glutinin molecules  are  cast-off  cell  receptors,  the 
overproduction  of  which  has  occurred  as  a  result  of 
their  union  with  the  agglutinogenic  molecules  of 
the  bacteria.     The  antitoxin  receptors  were  rela- 
tively simple,  having  no  other  demonstrable  struc- 
ture than  that  of  the  haptophorous  groups  through 
which  they  unite  with  the  corresponding  toxin. 
Receptors  of  We  have  recognized  in  the  agglutinin  receptor  two 

Second  Order.  i         i       ^  t~  ^  i        • 

groups,  a  haptophorous  and  a  zymotoxic;  conse- 
quently it  must  have  this  same  structure  when  it 
is  still  a  part  of  the  cell.  Ehrlich  designates  it  as 
a  receptor  of  the  second  order,  which,  being  de- 
fined, is  a  receptor  in  which  a  haptophorous  and  a 
zymotoxic  group  exist  as  integral  parts  of  the 
molecule  (Fig.  6). 

In  accordance  with  the  side-chain  theory,  the 
ability  of  an  animal  to  form  agglutinins  for  a  cer- 
tain organism  would  depend  on  its  possession  of  re- 
ceptors of  the  second  order  which  are  able  to  unite 
with  the  agglutinogenic  receptors  of  the  bacterium. 
It  is  well  established  that  different  animals  may 
not  form  serums  with  equal  agglutinating  powers 
for  an  organism.  The  follovdng  is  a  concrete  ex- 
ample: Wassermann  immunized  rabbits,  guinea- 
pigs  and  pigeons  with  a  strain  of  the  colon  bacil- 
lus, and  tested  the  three  serums  with  fifteen  other 
strains  of  the  same  organism.  The  serum  of  the 
guinea-pigs  readily  agglutinated  the  strain  which 
was  used  for  immunization,  but  scarcelv  affected 


INAOGLUT/XAJilL/ry. 


115 


the  others.  The  serums  of  the  rabbits  and  pigeons 
also  agglutinated  the  homologous  culture,  but  the 
coagglutinins  which  they  possessed  did  not  affect 
other  strains  equally.  Consequently,  it  was  sup- 
posed that  the  cells  of  the  three  animals  contained 
a  limited  number  of  receptors  in  common,  whereas 


Fig.  6. — Graphic  representation  of  receptors  of  the  second 
order  and  of  some  substance  uniting  with  one  of  them,  c, 
ceU  receptor  of  the  second  order  ;  d,  toxophore  or  zymophorous 
group  of  the  receptor ;  e,  haptophore  of  the  receptor ;  f,  food 
substance  or  product  of  bacterial  disintegration  uniting  with 
the  haptophore  of  the  cell  receptor.  From  Ehrlich's 
"Schlussbetrachtungen,"  Nothnagel's  System  of  Medicine, 
vol.    viii. 

other  receptors  which  were  present  in  one  of  the 
animals  were  largely  wanting  in  the  other  two. 

Inagglutinability  was  mentioned  as  a  charac- 
teristic of  certain  bacteria,  especially  the  bacillus 
of  Priedlander.  This  condition  is  much  more  im- 
portant   when    it    involves    an     organism    which 


Inagglutinabil- 
ity of  Some 
Organisms. 


IIU  IM'ECTIOX    AM)    IMMUXITY. 

usually  is  agglutinated  with  ease.  In  some  in- 
stances, the  typhoid  bacillus  when  freshly  culti- 
vated from  a  patient,  or,  indeed,  from  contami- 
nated water,  has  been  found  to  resist  agglutination 
by  a  strong  serum;  the  same  organism  after  a 
period  of  existence  on  artificial  media  becomes  ag- 
glutinable.  Widal  and  Sicard  noted  that  often  the 
serum  of  a  typhoid  patient  would  not  agglutinate 
the  bacillus  which  had  been  cultivated  from  the 
patient's  own  body,  although  the  same  serum 
would  agglutinate  laboratory  cultures.  Cultiva- 
tion of  the  typhoid  bacillus  at  42  C.  will  cause  it 
to  lose  its  agglutinable  property,  but  it  may  be  re- 
established by  subsequent  cultivation  at  lower 
temperatures.  It  seems  that  this  variation  must 
be  due  to  some  change  in  the  bacteria,  i.  e.,  in  the 
agglutinable  substance.  It  is  possible  that  the 
organism,  during  its  existence  in  the  animal,  be- 
comes immimized  against  the  action  of  the  agglu- 
tinin just  as  the  animal  becomes  immunized 
against  the  toxic  action  of  bacteria.  This  condi- 
tion in  the  micro-organisms  would  then  be  repre- 
sented by  a  great  excess  of  agglutinogenic  recep- 
tors, so  that  a  much  greater  amount  of  agglutinin 
would  be  required  to  cause  clumping.  It  is  read- 
ily seen  how  the  use  of  an  inagglutinable  strain  of 
the  t}'phoid  bacillus  would  affect  serum  diagnosis. 
Thftoriesof  We  are  to  consider  that  in  the  phenomenon  of 
agglutination  a  reaction  of  a  chemical  or  physico- 
chemical  nature  takes  place  between  the  agglutinin 
of  the  serum  and  the  agglutinogen  of  the  micro- 
organisms, the  actual  clumping  following  as  a 
consequence  of  this  reaction.  It  is  not  a  "vital'* 
reaction,  for  dead  bacteria  may  be  agglutinated. 


Agglutination. 


THEORIES    OF    A(J(JLUTINATION.  117 

Theories  of  agglutination  have  to  do,  not  with 
the  existence  of  agglutinin  and  agglutinogen,  but 
rather  with  the  nature  of  the  reaction  between  the 
two,  and  the  influences  which  bring  about  the 
clumping  after  the  reaction  has  occurred.  The 
original  theory  of  Gruber  supposed  that  the  serum 
so  affected  the  bacteria  that  they  became  sticky; 
consequently,  as  they  came  in  contact,  they  were, 
so  to  say,  glued  together.  Dineur  thought  changes 
occurred  in  the  flagells  of  the  organisms,  a  theory 
which  is  untenable  because  some  bacteria  are  ag- 
glutinable  which  do  not  possess  fiagellse.  Em- 
merich and  Loew  refer  agglutination  to  the  action 
of  an  enzyme  which  is  produced  by  the  bacterium 
itself,  a  theory  which  is  not  given  general  credence. 
Bordet  excludes  the  vitality  or  motility  of  the  or- 
ganisms as  factors,  and  believes  that  the  process  is 
purely  a  ph5^sical  one,  because  of  the  fact  that 
some  laiown  chemical  substances  may  be  made  to 
precipitate  or  to  agglutinate  certain  other  sub- 
stances (precipitation  of  colloids  by  salts)  ;  the 
theory  presupposes  some  change  in  the  molecular 
attraction  between  the  microbes  and  the  surround- 
ing fluid. 

Other  theories  have  to  do  with  the  question  of 
precipitation.  As  previously  stated,  when  the  fil- 
trates of  cultures  of  certain  organisms  are  mixed 
Avith  their  corresponding  immune  serums,  precipi- 
tates occur  in  the  mixtures.  It  was  mentioned 
that  the  substance  in  the  filtrate  which  takes  part 
in  the  precipitation  may  represent,  in  part,  the  ag- 
glu  tin  able  substance  which  has  been  excreted  by 
the  bacteria.  Mcolle  supposes  that  the  agglutin- 
able  substance  resides  in  the  external  layer  of  the 
bacteria  and  that  when  the  serum  is  added  a  coag- 


lis  IXFECrfOX  Axn  immtxity. 

ulation  occurs  in  tlie  envelope,  rendering  coales- 
cence with  the  envelopes  of  other  individuals  pos- 
sible. The  theory  of  Paltauf  that  the  agglutinable 
substance  finds  its  way  to  the  surface  of  the  bac- 
terium and  is  precipitated  by  its  union  with  ag- 
glutinin is  somewhat  similar.  The  shell  of  the  co- 
agulated substance  accounts  for  the  sticky  charac- 
ter which  the  envelope  acquires,  according  to  the 
theory  of  Gruber.  Paltauf  cites  observations 
which  tend  to  show  that  some  substance  actually 
is  extruded  from  the  micro-organisms  during  ag- 
glutination, and  that  in  properly  stained  speci- 
mens it  can  be  seen  as  a  precipitate  surrounding 
and  between  adjacent  organisms. 

The  multiplicity  of  theories  leads  one  to  suspect 
that  the  true  nature  of  the  process  remains  obscure. 


CHAPTER  XI. 


Precipitins. 


PRECIPITINS. 

Because  of  their  scientific  importance  and  cer- 
tain practical  features,  the  serum-precipitins 
should  receive  something  more  than  the  incidental 
mention  which  has  been  given  them  under  agglu- 
tination and  in  other  chapters. 

In  1897  Kraus  discovered  that  bouillon  cultures  Bacterial 
of  the  organisms  of  typhoid,  cholera  and  plague, 
from  which  the  bacteria  had  been  removed  by  fil- 
tration, would  cause  precipitates  when  mixed  with 
their  respective  antiserums.  The  reaction  is  spe- 
cific. As  stated  later,  however,  this  specificity 
holds  only  when  those  quantitative  relationships 
are  observed  which  were  found  so  essential  for  the 
agglutination  test.  The  precipitins  of  Kraus  are 
the  bacterial  precipitins.  He  proposed  their  use 
for  the  identification  of  micro-organisms.  If,  for 
example,  one  has  in  hand  a  culture  which  he  sus- 
pects to  be  that  of  the  typhoid  bacillus,  it  may  be 
gro^\ai  in  a  liquid  medium,  the  cells  removed  by 
filtration,  and  the  filtrate  mixed  with  a  Icnown 
antityphoid  serum;  if  a  precipitate  occurs  when 
the  serum  is  sufficiently  diluted,  the  reaction  indi- 
cates that  the  organism  in  question  is  the  typhoid 
bacillus.  Inasmuch  as  precipitins  are  formed  dur- 
ing the  course  of  some  infections  it  may  be  possible 
to  use  them  in  clinical  diagnosis,  but  for  either 
bacterial  or  clinical  diagnosis  the  agglutination 
test  is  more  readily  performed  and  interpreted. 


120 


INFECTION   AND    IMMUNITY. 


Phytoprecipi- 
tins  and  Zo- 
oprecipitins. 


Lactoserum. 


Precipitogen, 

Precipitin  and 

Precipitate. 


Pli}'toprecipitins  are  produced  by  immtmiza- 
tion  with  albuminous  substances  of  plant  origin, 
as  ricin  and  albumin  from  grains,  and  their  action 
is  specific  for  the  homologous  substance. 

Zooprecipitins  are  obtained  by  immunizing  with 
animal  albumins.  Through  the  work  of  Wasser- 
mann  and  Ulilenhuth,  of  ISTuttall,  and  others,  it 
luTs  been  demonstrated  as  a  general  law  that  im- 
munization with  an  albumin  from  whatsoever 
source  gives  rise  to  the  formation  of  a  precipitin 
which  manifests  its  action  only  against  the  par- 
ticular albumin  used  for  the  immunization.  Hence, 
the  albumin  of  a  particular  serum,  in  some  un- 
Icnovm  respect,  is  different  from  that  of  all  others ; 
it  is  special  to  the  species. 

Immunization  with  milk  causes  the  formation 
of  a  precipitin  which  throws  down  the  casein  of 
the  milk  used  for  injection,  but  not  that  of  milk 
from  another  species.  The  milk  of  the  goat  may 
be  differentiated  from  that  of  the  cow  by  the  use 
of  the  lactoserum. 

Likewise,  after  the  injection  of  egg-albumin  a 
precipitin  is  formed  which  is  specific  for  the  type 
injected. 

Three  substances  are  open  to  study  in  the  pre- 
cipitation reaction.  First,  the  fluid  or  substance 
which  is  used  for  immunization ;  it  bears  the  name 
of  precipitogen,  i.  e.,  the  precipitin-producing  sub- 
stance. Second,  the  specific  constituent  of  the 
precipitating  serum,  i.  e.,  the  precipitin.  Third, 
the  precipitate,  which  is  a  consequence  of  the  reac- 
tion between  precipitogen  and  precipitin.  We  are 
able  to  recognize  in  this  instance  the  actual  end- 
product  of  a  reaction,  a  condition  which  is  not  so 
easilv  realized  in  other  "immunitv  reactions."    Tt 


PEECIPiriN. 


121 


is  true,  of  course,  that  little  has  been  learned  con- 
cerning the  nature  of  the  end-product ;  its  chemis- 
try is  as  dark  as  that  of  the  proteids  in  general. 

As  stated  in  the  chapter  on  "Natural  Immun-  Formation  of 
ity/'  normal  serums  occasionally  have  the  power  *'''^*^""t'"- 
to  cause  precipitates  in  other  serums.  Precipitins 
for  egg  albumin  and  goat  serum  have  been  found 
in  extracts  of  organs,  although  at  the  same  time 
they  were  absent  from  the  serum  of  the  animal. 
In  this  case  the  active  bodies  exist  in  the  cells  as 
"sessile  receptors/'  and  by  the  process  of  extraction 
they  are  brought  into  solution.  During  immuniza- 
tion these  same  receptors  are  stimulated  to  over- 
production and  are  thrown  into  the  circulation  as 
free  precipitin  receptors. 

The  power  of  forming  precipitins  may  be  widely 
distributed  among  the  organs.  This  function  has 
been  assigned  to  the  leucocytes  (Kraus  and  Leva- 
diti,  Moll),  and  in  one  case  they  were  formed 
locally  in  the  anterior  chamber  of  the  eye  (v. 
Dungern.  Eomer). 

For  the  artificial  production  of  precipitins  the 
precipitinogenous  fluid  may  be  injected  into  the 
veins,  peritoneal  cavity  or  the  subcutaneous  tissue. 
Within  from  four  and  a  half  to  five  days  the  pre- 
cipitin has  been  formed  to  such  an  extent  that  it 
may  be  demonstrated  in  the  serum  of  the  im- 
munized animal. 

As  in  the  case  of  agglutinin  formation,  not  all 
animals  have  equally  the  power  of  forming  a  pre- 
cipitin for  a  given  albumin.  This  point,  as  re- 
lated to  serum  precipitins,  is  of  particular  impor- 
tance, and  involves  a  factor  which  is  of  no  conse- 
quence in  bacterial  agglutinins.  In  the  first 
place,  an  animal  will  not  form  a  precipitin  which 


Concerning 
Autoprecipi- 
tins  and  Iso- 
precipitins. 


ill  IXFKCTION  AM)  IM.MCMTY. 

'  is  active  against  its  own  serum,  i.  e.,  by  bleeding 
an  animal  and  reinjecting  the  serum  a  specific  pre- 
cipitin is  not  formed.  If  formed  it  would  be  an 
autoprecipitin,  and,  as  a  rule,  animals  do  not  form 
antibodies  for  their  own  tissue  constituents. 
Again,  animals  are  unlikely  to  form  antibodies  for 
the  tissue  constituents  of  other  members  of  the 
same  species;  these,  when  formed,  are  called  iso- 
bodies.  Schiitze  immunized  thirty -two  rabbits 
with  serum  from  the  rabbit  and  obtained  an  iso- 
precipitin  from  only  two  of  the  number.  In  the 
third  place,  animals  do  not  readily  form  anti- 
bodies for  the  tissue  constituents  of  other  animals 
which  zoologically  or  biologically  are  closely  re- 
lated. Immunization  of  the  guinea-pig  witli  the 
serum  of  the  rabbit,  a  pigeon  with  that  of  a 
chicken,  or  a  monkey  with  human  scrum,  are  pro- 
cedures which  usually  do  not  yield  precipitating 
scrums. 
Nature  of  Chemically,  little  is  laiown  of  precipitins.  They 
Precipitins.  ^^,^  thrown  down  by  ammonium  sulphate  in  con- 
jimction  with  the  euglobulin  fraction  of  serum,  and 
are  destro^'ed  by  those  substances  whieli  alter  al- 
buminous bodies,  as  acids,  alkalies,  pepsin  and 
trypsin. 
Specific  When  serum  is  heated  to  from  50°  to  60°  C.  its 
ability  to  cause  a  precipitate  in  the  homologous 
]n*ecipitogen  is  destroyed,  although  it  may  be  dem- 
onstrated that  the  power  to  combine  with  the  lat- 
ter is  unchanged.  Hence  precipitin,  like  agglu- 
tinin, is  composed  of  two  groups,  a  binding  or 
haptophorous.  and  a  ferment-like  group  in  which 
the  active  property  reside:  the  latter  is  the  cnag- 
ulin  of  the  molecule.  Wlien  precipitin  has  lost  its 
coagulin  it  becomes  prccipitoid.  and  as  precipitoid 


Inhibition. 


SPECIFIC  INN fJilTION. 


123 


it  may  unite  with  precipitogen  and  thoreljy  inhibit 
the  action  of  a  fresh  precipitin  which  may  be 
added  later.  When  a  precapitating  serum  has 
partly  degenerated  into  precipitoids,  that  is,  when 
it  consists  of  a  mixture  of  precipitin  and  precipi- 
toid,  it  is  found  that  the  latter  have  the  greater 
affinity  for  precipitogen;  hence,  in  concentrated 
solutions  of  the  serum,  precipitoid  may  be  present 
in  sufficient  quantity  to  bind  all  the  available  pre- 
cipitogen, and  the  reaction  w^ould  not  occur  in 
spite  of  the  presence  of  active  precipitin.  This  is 
spoken  of  as  specific  inhibition.  The  action  is 
analogous  to  that  of  toxoids  and  agglutinoids,  and 
the  phenomenon  is  mentioned  again  in  this  in- 
stance in  order  to  emphasize  the  fact  that  certain 
principles  of  action  are  common  to  many  of  the 
immune  substances.  Precipitoids,  like  toxoids  and 
agglutinoids,  are  formed  by  long  standing,  by  the 
action  of  heat  and  light  and  by  other  injurious  in- 
fluences. 

The  molecule  of  precipitin,  like  that  of  agglu- 
tinin, is  a  receptor  of  the  second  order  (Fig.  6). 

The  attempt  has  been  made  to  produce  antipre-  Antiprecipitins. 
cipitins  by  immunization  with  precipitating 
serums ;  this  is  immunization  with  an  immune 
serum.  It  is  reported  that  antibodies  have  been 
obtained  for  lactoserum,  but  not  for  bacterial  pre- 
cipitins. There  is  a  limit  to  the  cycle  of  antibody 
formation. 

Precipitogen  may  be  defined  as  any  albuminous 
substance  immunization  with  which  will  cause  the 
formation  of  a  specific  precipitating  serum.  In 
addition  to  those  mentioned  above,  albuminous 
urine,  pleural  exudates,  ascitic  fluid  and  that  from 
hydrocele  are  precipitogens.     The  same  is  true  of 


Nature  of 
Precipitogen. 


124  INFLCTIOX  AMJ  IMMLMTY. 

■  some  albuminous  fractions  of  scrums,  as  globulin. 
the  precipitating  serum  for  which  may  be  called 
antiglobulin.  Kraus  believes  that  the  precipitogen 
of  bacterial  filtrates  is  associated  with  albuminous 
molecules.  Jacoby  obtained  by  tryptic  digestion 
of  ricin,  a  precipitogen  which  gives  no  albumin 
reaction.  On  the  other  hand,  certain  precipito- 
gens  are  destroyed  by  pepsin  and  tr^npsin,  a  fact 
which  indicates  their  albuminous  nature. 

Certain  precipitogens  are  said  to  consist  of  a 
thermolabile  and  a  thermostabile  portion,  the  dif- 
ferentiation of  which  we  need  hardly  consider. 
Precipitoid  It  is  of  no  little  interest  that  precipitogen,  simi- 
Precipitogen!  lar  to  precipitin,  consists  of  two  groups,  through 
one  of  which  it  unites  with  precipitin,  whereas  the 
other  has  a  coagulating  function.  Egg  albumin, 
for  example,  when  heated  to  rather  high  tempera- 
tures, loses  its  ability  to  participate  in  the  pre- 
cipitation reaction,  although  it  retains  its  binding 
power  for  precipitin.  Tn  view  of  the  fact  that  the 
two  substances  which  enter  into  the  reaction  have 
similar  structures,  it  is  difficult  to  say  which  as- 
sumes the  passive  and  which  the  active  role.  De- 
generated precipitogen  is  also  called  precipitoid. 
Tn  order  to  distinguish  the  two  precipitoids  one 
mnst  speak  of  the  precipitoid  of  precipitogen.  and 
the  precipitoid  of  precipitin.  The  precipitoid  of 
precipitogen  yields  precipitin  by  immunization; 
hence,  it  is  all  the  more  analogous  to  the  toxoids. 
Precipitate.  The  •|)recipitatc  which  is  caused  when  a  bacterial 
filtrate  is  mixed  with  its  specific  antiserum  forms 
in  from  one-half  hour  to  several  hours,  and  appears 
as  a  coherent  white  sediment  which  in  the  course 
of  twenty-four  hours  has  left  the  overlying  fluid 
quite  clear.      The   action   of  the   precipitins   for 


FORENSIC  TESTS. 


125 


serums  is  more  rapid,  and  in  either  case  sedimen- 
tation is  hastened  by  placing  the  fluids  at  body 
temperature.  As  intimated  above,  the  occurrence 
of  the  reaction  depends  on  an  intact  condition  of 
the  coagulin  groups  of  both  substances.  A  low 
concentration  of  organic  acid  favors,  whereas  min- 
eral acids  and  alkalies  inhibit  or  prevent  precipi- 
tation ;  a  neutral  reaction  is  indifferent.  The  pre- 
cipitate contains  albumin,  which,  however,  has  be- 
come so  changed  that  it  is  not  susceptible  to  the 
action  of  trypsin.  The  two  in  combining  have  in 
some  way  shut  off  the  point  of  attack  for  tr}'psin. 
A  lactoserum  precipitates  the  casein  of  the  corre- 
sponding milk.  The  presence  of  salts  is  necessary 
for  the  reaction  of  precipitation. 

Group  precipitation  is  not  so  pronounced  as 
group  agglutination,  yet  it  exists  to  a  certain  de- 
gree and  is  of  the  utmost  practical  importance  in 
attempting  to  differentiate  serums  by  the  precipi- 
tation method.  Although  bacterial  precipitins  are 
highly  specific,  it  is  important  to  observe  the  prin- 
ciple of  serum  dilution  which  was  emphasized 
under  agglutination,  in  order  to  obtain  the  adven- 
titious precipitins  in  such  small  amounts  that 
they  do  not  interfere  with  the  chief  precipitin. 

That  feature  of  the  precipitation  reaction  which 
has  the  most  practical  bearing  has  to  do  with  its 
medicolegal  use  in  the  detection  of  human  blood. 
For  this  purpose  it  has  supplanted  the  specific 
hemolytic  serums,  which  are  to  be  referred  to  later. 
In  the  course  of  investigations  it  was  found  that 
even  the  smallest  dried  blood  stain,  although 
months  old,  would  cause  the  formation  of  a  sedi- 
ment when  mixed  with  its  homologous  precipitat- 
ing serum.    It  remained  for  certain  important  de- 


Group  Precipi- 
tation and 
Specificity. 


Forensic  Use 
of  Precipitins. 


l-2()  IXFECTIOy  AM>  IMMl  XITY 

tails  to  be  worked  out  in  order  to  render  the  test 
sufficiently  reliable  for  forensic  work.  The  spe- 
cificity of  the  reaction  appeared  to  be  threatened 
somewhat  wlien  it  was  learned  that  the  serum  of 
monkeys  under<?oes  precipitation  Avhen  treated  by 
an  immune  serum  which  is  specific  for  human 
serum.  Tliis  is,  again,  group  precipitation.  Ad- 
ventitious precipitation  is,  in  fact,  so  widespread 
that  some  have  felt  justified  in  speaking  of  a  mam- 
malian scrum  reaction.  Hence,  in  order  to  insure 
specificity,  it  has  become  necessary  to  use  precise 
quantitative  methods  in  differentiating  bloods  or 
serums  by  this  method.  The  immune  serum  which 
is  used  in  the  test  must  be  diluted  to  some  extent 
in  order  to  eliminate  accidental  precipitins :  hut 
even  a  more  important  precaution  is  the  volumet- 
ric measurement  of  the  precipitate  which  is 
formed.  The  technic  of  Schur  may  be  cited.  Test 
tubes  are  so  made  that  the  lowermost  portion  con- 
sists of  a  graduated  capillary  tube.  One  c.c.  of  the 
fluid  to  be  tested  is  placed  in  one  of  these  tubes,  to 
which  is  then  added  0.2  c.c.  of  the  precipitating 
serum.  The  mixture  is  kept  at  body  temperature 
until  the  reaction  is  complete,  and  the  sediment  is 
then  thrown  into  the  capillary  portion  of  the  tube 
by  centrifugation  for  a  stated  period  of  time 
(twenty  minutes).  The  volume  of  the  sediment 
may  be  read  by  the  scale.  Xuttall  allows  the  sedi- 
mentation to  occur  naturally,  Tvdth  the  tubes  in  an 
upright  position.  Other  serums  naturally  must 
be  used  as  controls.  If  the  "unknown"  blood  is 
suspected  of  being  human,  a  control  tube  must  be 
prepared  in  which  a  similar  amount  of  known  hu- 
man serum  is  submitted  to  the  same  test.  If  the 
two  tubes  vield    similar   amounts  of  precipitate 


RECOGNITION   OF  MEATH.  127 

when  they  are  treated  witli  0.2  c.c.  of  a  precipi- 
tin which  is  specific  for  human  serum,  the  identity 
of  the  "unlaiown"  blood  as  that  of  man  is  estab- 
lished. To  obtain  the  specific  precipitin  it  is  cus- 
tomary to  immunize  rabbits  with  human  serum  for 
several  weeks. 

Another  practical   feature  of  the  precipitation    identification 

.      .  of  Meats 

test  has  to  do  wdth  the  differentiation  of  meats.  A 
precipitogenous  substance  which  is  characteristic 
for  the  animal  may  be  extracted  or  pressed  from 
the  flesh,  and  will  yield  a  precipitate  when  it  is 
mixed  with  a  precipitin  of  homologous  nature. 
This  is  of  particular  interest  in  those  countries  in 
which  the  meat  of  the  horse  is  put  on  the  market 
as  a  substitute  for  that  of  beef. 

The  possible  relationship  of  precipitation  to  bac- 
terial agglutination  was  referred  to  in  the  chapter 
on  agglutination. 

In  view  of  the  fact  that  the  protoplasm  of  the   Colloids  and 

IT  1     II  n  •  i-x  1  (■  the  Reactions 

body  and  the  albuminous  constituents  ot  serum  of  immunity. 
have  a  close  relationship  to,  or  really  are,  colloids, 
investigators  have  studied  certain  reactions  which 
occur  among  the  known  colloids  with  the  expecta- 
tion that  the  reactions  of  protoplasm  and  those  of 
serums  would  receive  some  elucidation.  IsTot  much 
advancement  can  be  made,  however,  until  the  prop- 
erties of  colloids  are  more  thoroughly  understood. 
Substances  which  go  into  solution  were  classi- 
fied by  the  English  physicist,  Graham,  as  crystal- 
loids and  colloids.  Crystalloids  include  many  in- 
organic salts.  Usually  they  form  clear  solutions 
in  water  and  exert  osmotic  pressure,  supposedly 
because  of  the  small  size  of  their  molecules.  They 
diffuse  with  some  rapidity  and  many  are  conduc- 
tors of  electricity.    Organic  colloids  comprise  such 


128  INFECTION  AND  IMMUNITY. 

Properties  of  substancGs  iis  albuiiiiii,  starch,  dextrin,  tannin, 
gelatin  and  many  gums.  By  propex  treatment  of 
certain  metals  and  their  salts,  inorganic  colloids 
may  be  prepared ;  for  example,  ferric  hydroxid  and 
the  sulphids  of  antimony  and  arsenic.  Wlien  col- 
loids are  dissolved  in  water  the  solutions  are  often 
more  or  less  opaque,  and  are  sometimes  opalescent 
because  the  particles  or  molecules  are  of  such  size 
that  they  polarize  light.  They  exist  in  water  either 
as  a  solution  of  molecules  of  great  size  or  as  a  sus- 
pension of  considerable  particles  or  aggregates  of 
molecules.  In  some  instances  the  particles  are  so 
large  that  they  may  be  seen  by  a  magnification  of 
1.000  diameters,  while  in  others  no  degree  of  mag- 
nification renders  them  visible  ^^nih  the  ordinary 
microscope.  By  the  use  of  the  recently  devised 
ultramicroscope,  however,  the  finest  particles  in 
some  colloidal  solutions  may  be  discerned.  Col- 
loidal substances,  such  as  albumin,  diffuse  very 
slowly  and  exert  little  or  no  osmotic  pressure,  sup- 
posedly because  of  the  large  size  of  the  particles. 
They  do  not  conduct  electricity,  but  the  particles 
themselves  react  to  the  electric  current  by  altera- 
tions in  the  direction  of  their  motion  (i.  e.,  toward 
the  positive  or  the  negative  pole),  and,  moreover, 
carry  electric  charges  themselves. 
Precipitation  The  features  of  colloids  which  bring  them  into 
**Eimroiyt^^.  relation  with  the  subject  in  hand  are  their  coagu- 
lable  nature  in  certain  instances  and  the  fact  that 
their  particles  may  be  agglutinated  or  precipi- 
tated by  the  addition  of  minute  amounts  of  salts 
(electrol}i;es).  In  this  connection  one  naturally 
recurs  to  the  observation  of  Bordet,  which  was 
mentioned  in  the  preceding  chapter,  concerning 
the  inagglutinabilit^'  of  micro-organisms  so  long 


COLLOIDS.  129 

as  salt  is  withheld  from  the  solution.  This  anal- 
ogy would  suggest  that  the  bacteria  after  their 
union  with  agglutinin  may  conduct  themselves  as 
colloidal  particles.  In  the  precipitation  of  colloids 
by  salts  it  has  been  suggested  that  the  salts  so 
alter  the  electric  condition  of  the  colloidal  parti- 
cles that  their  surface  tension  is  decreased,  and  as 
a  result  of  this  change  neighboring  particles 
coalesce  in  such  quantities  as  to  produce  a  visible 
sediment. 

iSTeisser  and  Friedberger  have  studied  certain 
colloids,  having  in  mind  the  similarity  of  their  be- 
havior to  serum  reactions.  They  found,  for  exam- 
ple, that  two  of  our  common  dyes  which  are  col- 
loids and  bear  opposite  charges  of  electricity  (eosin 
and  Bismarck  browni),  give  rise  to  a  precipitate 
when  the  two  are  mixed.  Furthermore,  the  spe- 
cific inhibition  which  may  be  obtained  in  the  reac- 
tion with  serum  precipitins  (see  above)  could  also 
be  realized  with  the  eosin  and  Bismarck  brown. 

The  agglutination  of  bacteria  and  of  red  blood 
cells  may  also  be  accomplished  with  colloids. 
I^andsteiner  agglutinated  erythrocytes  with  col- 
loidal silicic  acid. 


CHAPTER  Xil. 


A.   OEXERAL   rROrEKTIES  OF  BACTERICIDAL 
SERUMS. 

Bacteriolysis  Antibacterial,  bactericidal  and  bacteriolytic  are 
lyslni  tliree  terms  which  are  used  in  a  rather  loose,  inter- 
changeable way,  although  they  are  not  strictly 
s}Tion}Tnous.  A  bactericidal  serum  is  one  which  is 
able  to  kill  bacteria,  as  the  term  implies ;  if  at  the 
same  time  it  dissolves  the  organisms  it  is  bacterio- 
l}-tic.  Inasmuch  as  some  serums  do  kill  bacteria 
without  dissolving  them  (typhoid),  while  others 
have  the  dissolving  power  (cholera),  the  distinc- 
tion has  a  certain  significance.  In  either  case  the 
serum  is,  of  course,  antibacterial.  For  lack  of  a 
more  concise  English  term,  bacteriolysis  is  Tised  to 
designate  the  process  in  which  bacteria,  with  or 
without  solution,  are  killed  by  serums.  Bacterioly- 
sin  refers  to  the  substances  in  serum  which  accom- 
plish this  action.  The  means  of  determining  the 
bactericidal  power  of  a  serum  were  indicated  in 
Chapter  V,  C.  True  bacteriolysis  is  best  observed 
with  the  organism  of  cholera  and  its  antiserum  as 
described  later  under  the  title  of  the  PfeifPer  ex- 
periment. 

Bacteriolysins  are  far  more  complex  than  anti- 
toxins, agglutinins  and  precipitins.  One  may  best 
appreciate  their  nature  as  understood  at  present 
b}''  tracing  their  development  from  the  relatively 
simple  alexins  of  Buchner. 
Alexins,  Following  the  investigations  of  Fodor,  Behring 
and  others,  which  showed  that  normal  blood  may 
kill  bacteria  in  the  test-tube,  and  after  additional 


ALEXINS.  131 

facts  were  obtained  by  Nuttall,  Buchner  demon- 
strated that  it  is  not  necessary  to  use  the  full  blood 
in  order  to  obtain  the  bactericidal  action,  but  that 
serum  alone  has  a  similar  effect.  He  spoke  of  the 
antibacterial  substances  collectively  as  alexins 
(substances  which  ward  off),  taking  the  reason- 
able view  that  natural  immunity  to  bacteria  de- 
pends on  their  presence  in  the  body.  The  increased 
bactericidal  power  of  the  serum  which  develops 
during  immunization  or  infection  with  certain 
micro-organisms  goes  hand  in  hand  with  the  in- 
creased resistance  of  the  individual  ^.gainst  the 
infection.  The  alexins  have  undergone  a  specific 
increase;  they  are  now  immune  alexins  or,  as  we 
say  to-day,  immune  bacteriolysins,  and.  it  is  sup- 
posed that  acquired  immunity,  in  these  instances, 
depends  on  their  new  formation. 

Alexins  were  very  sensitive  substances ;  they  dis-  selective 
appeared  spontaneously  from  serums  in  a  few  '^*'**"' 
days,  were  destroyed  by  a  rather  low  degree  of 
heat  (55°  C),  by  acids  and  alkalies,  and  were 
active  only  in  the  presence  of  certain  salts,  espe- 
cially sodium  chlorid.  A  striking  feature  of 
alexins,  as  distinguished  from  chemical  bacteri- 
cides, was  their  marked  selective  action  on  bac- 
teria. The  alexins  of  animal  A  might  destroy  one 
micro-organism  readily  and  affect  another  little  or 
none  at  all,  whereas  those  of  animal  B  might  have 
different  selective  characteristics. 

Work  which  was  instituted  by  Pfeiffer  and  de-   ThePhenome- 
veloped  further  by  others  led  the  way  to  a  more   "**"  "^  p^®'"^''- 
correct  understanding  of  the  nature   of   alexins. 
Pfeiffer  studied  the  bactericidal  action  of  serums 
in  the  body  of  the  living  animal,  i.  e.,  in  the  peri- 
toneal cavitv.     His  most  classic  results  were  ob- 


132  lyFECTION  AND  IMMUNITY. 

tained  with  the  organism  of  cliolera.  A  guiuea- 
pig  is  immunized  against  tliis  microbe  by  injec- 
tions of  the  killed  or  living  organisms.  We  have 
already  learned  of  this  process  as  that  of  active 
antibacterial  immunization.  When  the  animal  is 
Avell  immunized  the  experiment  is  begun  by  the 
intraperitoneal  injection  of  a  quantity  of  culture 
which  would  be  fatal  to  an  unimmimized  animal. 
At  intervals  during  the  next  twenty  or  thirty  min- 
utes small  amounts  of  peritoneal  fluid  are  removed 
for  .micToscopic  examination  by  means  of  fine 
pipettes  which  have  been  drawn  out  in  the  flame. 
The  abdominal  wall  is  punctured  with  the  pi- 
pette through  an  incision  in  the  skin  and  the 
fluid  flows  into  the  tube  by  capillary  attraction. 
A  portion  of  the  fluid  is  examined  as  a  hanging- 
drop  or  dried  on  a  cover-glass,  fixed  in  the  fiame 
and  stained  with  a  dilute  solution  of  carbol- 
fuchsin.  In  the  hanging-drop  it  is  first  noticed 
that  the  organisms  have  lost  their  motility;  the 
comma-  and  S-shaped  forms  soon  become  spherical 
and  at  first  appear  swollen  and  clear,  whereas  in 
later  preparations  they  gradually  decrease  in  size 
and  show  a  very  rapid  vibrating  movement,  the  so- 
called  Bro"v\aiian  movement,  which  is  purely  physi- 
cal in  nature.  In  the  course  of  from  twenty  to 
thirty  minutes  the  organisms  have  been  completely 
dissolved.  These  changes  may  be  followed  in  the 
stained  specimens,  in  which  the  altered  cells  event- 
ually appear  as  fine  red  granules. 
The  Experiment  As  Mctchnikoff,  Bordct  and  others  have  shown, 
the  same  result  may  be  obtained  without  the  inter- 
vention of  the  animal  body,  by  mixing  perfectly 
fresh  anticholera  serum  with  the  vibrios  and 
mounting   as   a  hanging-drop   preparation.      The 


Tissues. 


PFEIFFEIi  EXPFIilMENT.  133 

slide  must  be  kept  at  the  temperature  of  the  body 
by  means  of  a  warm  stage.  The  reaction,  how- 
ever, is  far  less  vigorous  than  when  it  takes  place 
in  the  peritoneal  cavity  and  the  solution  of  the 
cells  may  not  be  complete.  No  bacterium  is  so 
completely  dissolved  under  these  conditions  as  the 
vibrio  of  cholera,  although  the  typhoid  bacillus  and 
similar  organisms  undergo  some  changes  in  their 
form. 

The  experiment  of  Pfeiffer  may  also  be  con-  The  Activation 
ducted  in  the  abdominal  cavity  of  a  non-immune  senim"byVhe 
guinea-pig  by  injecting  anticholera  serum  in  con- 
junction with  the  culture  (passive  antibacterial 
immunization) .  This  is  the  classic  Pfeiifer  experi- 
ment. The  immune  serum  should  be  of  such 
strength  and  should  be  given  in  such  quantity  that 
the  animal  is  saved  in  spite  of  the  ten  fatal  doses 
of  culture  which  the  typical  experiment  demands. 
Experiments  brought  to  light  a  condition  which 
seemed  paradoxic;  an  old  immune  serum  which 
had  lost  its  bactericidal  power  as  manifested  in 
vitro,  or  one  in  which  the  alexins  had  been  de- 
stroyed by  a  temperature  of  60°  C,  showed  its 
original  protective  power  in  the  animal  experi- 
ment. Furthermore,  when  an  inactive  immune 
serum  was  injected  into  the  abdominal  cavity,  al- 
lowed to  remain  for  a  time  and  then  withdrawn, 
its  bactericidal  power  for  experiments  in  vitro  was 
found  to  be  re-established.  On  the  basis  of  these 
facts,  Pfeiffer  concluded  that  the  specific  sub- 
stance is  present  in  the  immune  serum  in  an  inac- 
tive form,  and  that  it  becomes  active  as  a  result 
of  contact  with  living  tissue  cells,  supposedly  the 
endothelial  cells  of  the  peritoneum.  According  to 
this  conclusion,  an  inactive  serum  could  become 


134 


ixrt:cTn)\  A\n  lUMUXirY. 


tnactivation 
and  Reacti- 
vation. 


Two  Substances 
in  a  Bacterici- 
dal Serum. 


active  again  only  after  its  introduction  into  the 
bod}'. 

Tt  remained  for  Bordet  to  sliow,  on  tlic  con- 
irnrv.  tliat  contact  of  the  serum  with  living  cells 
was  not  necessary  to  render  it  active  for  bacterici- 
dal experiments  in  vitro.  It  was  sufficient  to  add 
to  the  heated  immune  serum  a  small  amount  of 
fresh  normal  serum  from  some  normal  animal, 
the  quantity  of  normal  serum  which  was  used  not 
being  in  itself  bactericidal.  Under  these  condi- 
tions, then,  we  have  to  do  with  two  serums  which, 
when  combined,  are  bactericidal,  but  when  sepa- 
rated are  inactive.  The  destruction  of  the  active 
property  of  a  serum  by  heat  or  by  other  means  is 
called  inactivation,  and  the  re-establishment  of  its 
power  by  the  addition  of  fresh  normal  serum  is 
reactivation.  The  immune  serum,  when  heated  to 
55  to  60°  C,  loses  something  which  is  essential  to 
its  activity,  and  this  something  may  be  replaced 
by  the  normal  serum.  That  the  substance  in  the 
normal  serum  is  identical  with  that  which  was  de- 
stroyed in  the  immune  serum  is  indicated  by  the 
fact  that  it  is  destroyed  by  the  same  degree  of 
heat;  a  heated  normal  serum  will  not  reactivate 
an  immune  serum. 

The  conclusion  of  Bordet  that  the  bactericidal 
power  of  a  serum  depends  on  the  combined  action 
of  two  substances  has  been  substantiated  by  numer- 
ous investigators.  These  arc  the  sulistances  which 
in  recent  years  have  become  faiuiliar  under  the 
names  of  amboceptor  and  comjilement  and  tlicir 
various  SATionyms  (see  p.  1-llff).  One  of 
them,  the  amboceptor,  is  heat-resistant  (thermo- 
stabile).  i.  e.,  it  is  not  destroyed  at  56°  C,  whereas 
the  other,  the  complement,  is  susceptible  to  heat 


GROUP  REACTION. 


135 


(thermolabile),  being  destroyed  at  that  tempera- 
ture which  killed  the  alexins  of  Buchner.  The 
term  alexin  is  still  applied  by  some  writers  to  the 
thermolabile  substance  (complement),  its  original 
significance  having  been  modified. 

The  specificity  which  prevails  among  antitoxins  Specificity. 
and  agglutinins  is  found  also  in  the  action  of  bac- 
tericidal serums.  When  an  anticholera  serum  is 
injected  into  the  peritoneal  cavity  of  a  guinea- 
pig,  protection  is  not  afforded  against  other  vibrios 
or  other  pathogenic  organisms.  The  specificity  is 
so  great  that  the  re'action  of  Pfeiffer  may  be  used 
for  the  identification  of  bacteria.  If  one  has  in 
hand  an  unknown  vibrio,  its  identity  or  non-iden- 
tity as  the  organism  of  cholera  may  be  determined 
by  injecting  it,  in  conjunction  with  anticholera 
serum,  into  the  peritoneal  cavity  of  a  normal 
guinea-pig;  if  the  microbe  is  transformed  into 
granules  it  is  the  vibrio  of  cholera,  otherwise  it  is 
not.  Other  bacteria  may  be  identified  in  a  similar 
manner  by  the  use  of  the  proper  serums.  In  spite 
of  this  high  specificity,  the  group  reaction  may 
occur  even  with  bactericidal  serums.  An  anti- 
typhoid serum,  for  example,  shows  its  strongest 
bactericidal  power  for  the  typhoid  bacillus,  al- 
though it  is  at  the  same  time  more  destructive  for 
closely  related  organisms,  as  the  colon  bacillus, 
than  a  normal  serum  from  the  same  species.  By 
diluting  the  serum  suffieientl}^  the  adventitious 
bacteriolysins  are  so  nearly  eliminated  that  the 
specificity  of  the  serum  for  its  homologous  organ- 
ism becomes  manifest. 

Bactericidal  serums  are  not  obtained  with  equal 
readiness  for  all  micro-organisms.  We  are  most 
familiar  with  those  which  are  yielded  by  immuni- 


Group 
Reaction. 


The  Bacterici- 
dal Power  in 
Relation  to 
Immunity. 


13G  I^'FECTION  AyO  IMMUNITY. 

zation  or  infection  "with  tlie  microbes  of  cholera, 
typhoid,  plague,  the  colon  bacillus  and  related  bac- 
teria. Many  other  bacteria,  as  the  pneumococcus, 
streptococcus,  tubercle  bacillus  and  others,  yield 
.  neither  antitoxins  nor  bactericidal  substances.  In- 
asmuch as  recovery  from  such  infections  is  an  ex- 
pression of  acquired  immunity,  no  matter  how 
temporary  it  may  be,  it  is  evident  that  not  all  ex- 
amples of  acquired  immunity  can  be  explained  on 
the  basis  of  the  serum  properties  which  we  now 
recognize  (see  Chapter  V,  C).  This  will  be  re- 
ferred to  again  in  relation  to  phagocytosis  (Chap- 
ter XIY). 

Experiments  of  some  importance  have  to  do 
with  the  ability  of  bacteria  to  absorb  the  homolo- 
gous bactericidal  substance  from  a  serum  when  the 
two  are  mixed  in  test-tubes.  Hence,  if  natural 
antibacterial  immunity  depends  on  the  bacterioly- 
sin  which  is  present  in  the  circulation,  a  large 
mass  of  the  bacterium  when  injected  intravenously 
should  absorb  or  fix  the  bactericidal  substances ;  as 
a  consequence,  serum  which  is  dra^vn  later  should 
show  a  great  decrease  in  its  bactericidal  power  for 
the  organism  which  was  injected.  Although  re- 
sults of  this  nature  have  been  obtained  by  a  num- 
ber of  competent  investigators,  they  are  not  with- 
out exception.  In  the  same  connection  fatal  infec- 
tions should  be  accompanied  by  a  decrease  of  the 
natural  bactericidal  power  of  the  serum  for  the 
organism  involved.  This  has  been  found  to  be  true 
in  man  in  relation  to  plague,  and  in  some  animal 
infections. 
The  Effect  of  In  a  preceding  chapter  micro-organisms  were 
^erums"on  divided,  first,  into  those  which  secrete  soluble  tox- 
Endotoxins.   ^^^^  immunization  with  which  causes  the  forma- 


EFFECT  ON  ENDOTOXINS.  137 

tion  of  antitoxins,  and,  second,  those  which  do  not 
secrete  such  toxins  and  for  which  no  manipula- 
tions known  at  the  present  time  are  successful  in 
stimulating  to  the  formation  of  antitoxins.  These 
lines,  however,  can  not  be  drawn  sharply,  for  there 
are  a  few  microbes  which,  according  to  manipula- 
tion, cause  the  formation  of  either  an  antitoxic 
serum  or  a  bactericidal  serum.  In  general  it  may 
be  said  that  the  character  of  the  serum  depends  on 
the  bacterial  constituent  which  is  used  for  immuni- 
zation. If  the  diphtheria  bacillus  itself,  or  the 
pyocyaneus  bacillusj  is  injected,  the  toxin  having 
been  washed  away,  bactericidal  serums  are  formed, 
whereas  if  toxins  alone  are  introduced,  antitoxins 
are  the  result.  After  all,  it  seems  plain  that  the 
bacteria  of  the  second  'group  must  be  pathogenic, 
because  of  toxic  substances  which  they  carry  with 
them  into  the  body.  In  view  of  the  fact,  however, 
that  they  do  not  secrete  soluble  toxins  in  culture 
media,  it  is  held  that  their  toxic  properties  are  in- 
tegrally associated  with  the  bacterial  protoplasm; 
they  are  the  endotoxins  spoken  of  previously. 

The  question  naturally  arises :  Does  a  bacteri- 
cidal serum  in  dissolving  or  killing  its  homologous 
organism  neutralize  the  endotoxin  at  the  same 
time?  On  the  basis  of  very  positive  experiments 
which  have  been  performed,  especially  by  Pfeiffer, 
it  is  evident  that  the  serum  has  no  such  action.  In 
the  experiment  of  Pfeiffer,  one  may  inject  into  the. 
abdomen  a  sufficient  quantity  of  anticholera  serum 
to  kill  all  the  organisms  which  have  been  intro- 
duced, and  yet  the  animal  may  die  with  the  intoxi- 
tion  of  cholera.  Furthermore,  if  one  considers  a 
cvTlture  of  the  cholera  vibrio,  which  has  been  killed 
b}'  heat,  as  representing  so  much  cholera  toxin. 


138 


INFECTION  AND  IMMUNITY 


Origin  of 
Bactericidal 
Substances. 


Standard- 
ization. 


antieholera  sorum  protects  against  no  more  of  it 
than  does  the  same  qiiantitv  of  normal  serum.  It 
is  believed  that  antieholera  and  simihir  immune 
serums  may  even  increase  intoxication  by  dissolv- 
ing the  bacteria  and  thus  liberating  an  excess  of 
endotoxin. 

We  have  little  positive  knowledge  concerning  the 
organs  which  form  the  bactericidal  substances  in 
acquired  immunity.  Pfeiffer  and  Marx,  in  rela- 
tion to  cholera,  and  Wassermann  in  typhoid,  found 
that  the  spleen  and  the  hemopoietic  organs  in  gen- 
eral contain  the  immune  bodies  in  greater  concen- 
tration than  the  blood  serum,  and  in  immunization 
experiments  the  bodies  may  be  demonstrated  in 
these  organs  at  a  time  when  they  are  absent  from 
the  circulation.  This  fact  is  generally  accepted  as 
proof  of  their  formation  at  these  points.  Wasser- 
mann and  others  have  demonstrated  the  presence 
of  complement  in  the  leucoc3i:es,  and  IMetchnikoff 
holds  that  it  is  produced  only  by  such  cells. 

The  standardization  of  bactericidal  serums  is  at 
present  more  of  theoretical  than  of  practical  in- 
terest, because  of  their  limited  therapeutic  use. 
Their  values  can  not  be  determined  with  the  ac- 
curacy with  which  one  measures  a  unit  of  anti- 
toxin. One  may  deliver  from  a  pipette  a  definite 
quantity  of  toxin  and  if  the  toxin  has  been  well 
preserved  the  same  quantity  may  be  obtained  at 
any  subsequent  time.  On  the  other  hand, it  is  impos- 
sible to  preserve  a  culture  of  living  bacteria  so  that 
the  numl:)er  of  the  organisms  and  the  virulence 
of  the  culture  remain  constant,  nor  will  two  cul- 
tures made  at  different  times  contain  the  same 
number  of  cells  in  a  given  volume.  Hence,  stand- 
ard cultures  which  are  necessary  for  the  systematic 


STANDA  IWIZA  TfON.  139 

valuation  of  serums  are  not  easily  available.  One 
may  use  a  definite  volume  of  a  bouillon  culture  of 
an  organism  wbich  has  grown  for  a  certain  number 
of  hours,  but  in  all  likelihood  no  two  cultures 
would  contain  the  same  number  of  organisms. 
Pfeiffer  uses  the  normal  loop  which  has  been  men- 
tioned, i.  e.,  one  which  will  take  up  from  a  surface 
of  agar  two  milligrams  of  the  bacterial  mass.  The 
culture  must  have  grown  for  a  definite  period, 
eighteen  to  twenty-four  hours.  Tests  having  some 
value  may  be  made  in  the  test-tube  with  the  fresh 
or  complemented  serum.  This,  however,  gives  one 
only  the  bactericidal  power  as  it  is  manifested  out- 
side the  body,  and  it  may  not  be  a  correct  index  of 
the  protective  power  of  the  serum  when  it  is  in- 
jected into  the  living  animal.  For  the  test-tube 
experiment  various  dilutions  of  the  serum  are 
made,  as  1  to  10,  1  to  100  and  1  to  1,000,  and  a 
similar  quantity  of  each  dilution,  properly  comple- 
mented, is  mixed  with  a  given  mass  of  the  culture ; 
the  mixtures  are  then  placed  in  the  thermostat  for 
a  number  of  hours.  At  the  end  of  this  time  plate 
cultures  are  made  from  each  of  the  mixtures,  the 
plates  put  aside  for  twenty-four  hours,  and  the 
colonies  which  have  developed  are  then  counted. 
The  quantity  of  serum  required  to  kill  all  the  bac- 
teria may  be  taken  as  the  basis  for  computing  its 
bactericidal  value. 

When  the  protective  power  of  the  serum  is  de- 
termined by  animal  experiment  it  is  not  essential 
to  use  the  serum  when  fresh;  in  fact,  the  native 
complement  in  the  immune  serum  may  be  disre- 
garded, or,  preferably,  it  may  be  destroyed  by  heat. 
If  the  latter  procedure  is  adopted,  or  if  an  old 
serum  is  used  in  which  the  complement  has  de- 


140  INFECTIOX  A\D  IMMlXlTy. 

generated,  its  reactivation  is  accomplished  through 
the  complement  wliicli  is  present  in  the  hody  of  the 
experiment  animal.  It  will  appear  in  more  detail 
in  the  following  pages  that  a  given  antiserum  re- 
quires a  particular  complement  for  its  reactiva- 
tion, and  tliat  this  complement  may  he  present  in 
some  animals  and  absent  in  others. 

To  find  the  value  of  anticholera  serum  Pfeiffer 
prepares  dilutions  similar  to  those  mentioned 
above,  and  to  the  same  quantity  of  each  dilution 
adds  ten  fatal  doses  of  a  virulent  culture  of  the 
vibrio  of  cholera.  These  are  injected  into  the 
peritoneal  cavities  of  guinea-pigs  and  after  periods 
of  forty  to  sixty  minutes  hanging-drop  prepara- 
tions are  made  from  the  peritoneal  fluid  of  each 
animal  to  determine  the  formation  of  the  charac- 
teristic granules ;  the  highest  dilution  which  causes 
this  change  in  the  cells  stamps  the  value  of  the 
serum.  The  animal  must  at  the  same  time  be  pro- 
tected against  the  ten  fatal  doses  of  the  culture. 

The  value  of  an  antityphoid  serum  may  be  de- 
termined in  the  same  way,  the  result  being  judged 
by  the  protection  which  is  afforded  the  animal 
rather  than  by  the  formation  of  granules. 

Antityphoid,  antiplague,  and  some  other  serums 
are  also  tested  by  injecting  the  serum  twenty-four 
hours  in  advance  of  the  culture. 

It  is  necessary  to  Icnow  the  virulence  of  a  cul- 
ture with  which  an  antiserum  is  tested.  It  is  pos- 
sible to  maintain  some  organisms  at  a  rather  con- 
stant virulence  by  passage,  i.  e.,  infecting  animals 
"with  the  microbe  and  recultivating  it  from  the 
tissues.  With  others,  abundant  controls  must  be 
made  at  the  time  the  serum  is  tested  in  order  to 
know  at  that  moment  the  nrecise  virulence  of  the 


AMBOCEPTOR  AND  COMPLEMENT.  141 

culture.  In  all  probability  it  requires  more  serum 
to  protect  against  very  virulent  cultures  than 
against  those  of  less  virulence. 

In  contrast  to  the  specific  immunization  which   Non-specific 

,.,,..,  .  .,     Increase  in 

may  be  accomplished  with  an  immune  serum,  it  Resistance. 
is  important  to  recognize  that  a  non-specific  in- 
crease in  resistance  may  be  caused  by  the  injection 
of  a  number  of  substances,  which  in  the  test-tube 
have  no  destructive  action  on  the  bacteria.  Issaeff 
injected  into  the  peritoneal  cavity  such  substances 
as  bouillon,  tuberculin  and  sterile  urine,  and  found 
the  resistance  of  the  animals  increased  to  perito- 
neal inoculation  of  virulent  organisms.  Normal 
serum  from  another  animal  has  a  similar  effect, 
but,  in  this  instance,  the  bactericidal  substances  of 
the  foreign  serum  may  be  a  factor  in  the  new  re- 
sistance. Supposedly,  this  non-specific  resistance 
is  local,  and  it  appears  to  depend  on  the  attraction 
of  an  increased  number  of  phagocytes  and  of  addi- 
tional complement  to  the  peritoneal  cavity.  The 
suggestion  recently  made  that  preceding  laparot- 
omy nucleinic  acid  be  injected  into  the  abdominal 
cavity,  in  order  to  increase  the  local  resistance,  has 
its  foundation  in  the  experimental  work  just  cited. 

B.    AMBOCEPTORS    AND    COMPLEMENTS. 

The  simplicity  of  hemolytic  experiments  and  the  Experimental 
rapidity  with  which  they  may  be  performed  and  oi^si^s.  **"' 
terminated  have  rendered  hemolytic  serums  par- 
ticularly useful  in  the  study  of  amboceptors  and  of 
complements,  for  we  are  to  understand  that  such 
serums  are  toxic  to  erythroc}^es  only  because  of 
the  amboceptors  and  complements  which  they  con- 
tain. The  most  important  facts  which  have  been 
learned  concerning  the  action  of  hemolvtic  serums 


Technic  of 
Hemolytic 


142  lyFECTIOX  .WD  IMMLMTY. 

have  been  found  to  liold  true  for  bactericidal 
serums  as  well ;  hence  it  is  an  indifferent  matter 
if  principles  which  are  common  to  both  are  illus- 
trated by  frequent  references  to  serum-hemolysins. 
The  corpuscles  for  hemolytic  experiments  are 
Experiment,  obtained  by  the  defibrination  of  f^cshly-dra^\^l 
blood  and  the  removal  of  the  fibrin.  Usually  they 
are  made  into  a  5  per  cent,  suspension  by  dilution 
witli  isotonic  (physiologic)  salt  solution.  Inas- 
much as  the  serum  which  is  present  may  interfere 
with  the  action  of  the  complement  or  amboceptors 
of  the  hemolysin,  it  is  customary  to  remove  it  by  a 
washing  process.  The  5  per  cent,  emulsion,  or  the 
undiluted  blood  is  centrifugated,  the  overlying 
fluid  drawn  off  by  means  of  a  pipette  and  substi- 
tuted by  fresh  salt  solution;  the  corpuscles  are 
thoroughly  mixed  with  the  new  solution  and  the 
process  of  centrifugation  repeated,  the  corpuscles 
finally  being  diluted  to  the  original  volume  with 
salt  solution.  After  from  two  to  four  washings 
any  residual  serum  usually  may  be  disregarded. 
To  test  the  hemolytic  power  of  a  serum  one  meas- 
ures identical  quantities  of  the  5  per  cent,  washed 
blood  into  each  of  a  series  of  test-tubes  by  means 
of  a  graduated  pipette  and  then  adds  increasing 
quantities  of  the  serum  to  succeeding  tubes.  All 
tubes  are  then  diluted  to  equal  volumes  by  means 
of  salt  solution,  as  it  is  of  some  importance  to 
maintain  a  uniform  concentration  of  the  cor- 
puscles. The  contents  of  the  tubes  are  mixed 
evenly  by  shaking  and  the  series  is  placed  in  the 
thermostat  for  about  two  hours;  this  temperature 
is  necessary  for  complete  and  rapid  action  of  the 
toxic  substances.  At  the  end  of  this  time  the  tubes 
are  placed  in  the  ice  chest  and  left  over  night  in 


HEMOLYSIS. 


143 


order  that  the  cells  may  settle  to  the  bottom,  or 
sedimentation  may  be  accomplished  at  once  by 
centrifugation. 

In  either  case,  the  overlying  fluid  is  colored  red  Hemolysis. 
by  the  dissolved  hemoglobin  in  proportion  to  the 
extent  of  destruction  of  the  erythrocytes.  In  case 
solution  has  been  complete,  the  sediment  is  indis- 
tinct and  colorless,  being  made  up  only  of  the 
stromata  of  cells,  whereas  in  the  tubes  showing 
only  partial  hemolysis  the  sediment  is  red  and  has 
an  indirect  quantitative  ratio  to  the  coloration  of 
the  overlying  fluid. '  By  suitable  variations  in  the 
amounts  of  serum  used  in  difi'erent  tubes,  its 
exact  dissolving  dose  for  the  given  volume  of  cor- 
puscles may  be  determined.  Although  the  term 
hemolysis  is  a  perfectly  proper  one,  we  are  to  un- 
derstand that  serums  cause  solution  of  the  hemo- 
globin, but  not  solution  of  the  whole  cell ;  we  speak 
loosely  of  solution  of  the  corpuscles. 

After  Bordet  had  shown  the  analogy  between  similarity  Be-_ 
bactericidal  and  hemolytic  serums,  and  after  the  cidaj  and, Hem- 
phenomena  of  inactivation  and  reactivation  had  "^"^ 
been  developed  by  Bordet  and  Metchnikoff,  Ehrlich 
and  Morgenroth  tmdertook  the  study  of  ambocep- 
tors and  complements  as  they  occur  in  hemolytic 
serums.     The  facts  ascertained  by  them  and  the 
methods  of  research  which  they  devised  have  pro- 
vided many  investigators  with  a  starting  point  for 
work  of  the  highest  importance  concerning  the 
bactericidal   serums   and   antibacterial   immunity, 
and  their  interpretations,  moreover,  served  to  ex- 
tend the  side-chain  theory  of  immunity  to  its  pres- 
ent comprehensive  limits. 

For  the  sake  of  convenience  one  may  speak  of  a 
heated  immune  serum,  or  one  in  which  the  com- 


144  INFECTION  AND  IMMUNITY. 

Solutions  oi  plenient  lias  become  inactive  from  age,  as  a  solu- 
flird**comp*ie-  tion  of  amboceptops,  disregarding  temporarily  tbe 
ments.  agglutinins,  precipitins  and  perhaps  other  bodies 

which  the  serum  contains.  Also,  since  fresh  nor- 
mal serums  are  rich  in  complements  and  usually 
contain  but  a  small  amount  of  any  one  amboceptor, 
they  may  conveniently  be  considered  as  solutions 
of  complements;  3'et  normal  serums  may  not  be 
considered  as  pure  complement  and  used  as  such 
in  unlimited  quantities  for  actiuil  experiments,  be- 
cause of  the  bacteriolysins  and  hemolysins  which 
many  contain.  Only  a  quantity  of  the  normal 
serum  which  in  itself  is  not  toxic  for  the  cell 
may  be  used  for  complementing  purposes,  and  this 
may  be  as  low  as,  or  lower  than,  0.1  c.c.  for  a  par- 
ticular experiment. 
The  Absorption       As  pointed  out  in  the  preceding  chapter,  the 

of  Amboceptors  i-ni-  t>  i  i  i  i  i_   • 

by  Cells.  combmed  action  ol  amboceptor  and  complement  is 

necessary  for  the  cytotoxic  action  of  a  serum.  In 
view  of  the  fact  that  the  toxic  power  is  lost  by  ex- 
posure to  that  temperature  which  destroys  comple- 
ment, it  seems  that  the  latter  is  the  actual  dis- 
solving or  toxic  substance,  whereas  the  ambocep- 
tor must  play  some  intermediary  role.  Investiga- 
tions have  shown  that  the  two  act  together  in  a 
very  definite  manner  in  that  the  absorption  of  the 
amboceptors  by  the  cells  is  a  prerequisite  for  the 
absorption  and  action  of  the  complement.  This 
may  be  verified  by  simple  experiments.  Mix 
erythroc3i;es  with  the  homologous  amboceptors, 
and  after  a  period  of  from  twenty  to  thirty  min- 
utes centrifugate  the  mixture  and  remove  all  the 
free  serum  from  the  cells  by  repeated  washings 
with  isotonic  salt  solution.  If  the  cells  are  again 
suspended  in  salt  solution  and  a  small  amount  of 


MECEAISIIBM    OF   HEMOLYSIS.  145 

complement  is  added  and  thoroughly  mixed,  the 
hemoglobin  is  dissolved  out;  a  control  must,  of 
course,  show  that  the  complement  alone  has  not 
the  dissolving  power.  The  result  indicates  that 
the  erythrocytes  during  their  contact  with  the  im- 
mune serum  had  absorbed  or  combined  chemically 
with  the  amboceptors,  and  that  the  latter  remained 
attached  to  the  cells  in  spite  of  the  washings  to 
which  they  were  submitted.  < 

It  would  seem  that  the  union  of  amboceptor  Sensitization 
with  cell  has  the  effect  of  rendering  the  latter  sus- 
ceptible to  the  action  of  complement,  and  for  this 
reason  amboceptor-laden  cells  are  spoken  of  as 
sensitized  cells.  Hence,  according  to  the  cells  and 
serums  employed,  we  may  refer  to  sensitized 
erythrocytes,  sensitized  bacteria,  etc.  The  experi- 
ment is  called  the  sensitizing,  absorption  or  bind- 
ing experiment.  An  immune  serum  may  be  de- 
prived of  all  its  amboceptors  in  the  binding  ex- 
periment if  a  sufficient  quantity  of  cells  has  been 
used,  and  it  would  thereby  be  rendered  incapable 
for  further  reactivation  by  the  subsequent  addition 
of  complement. 

If,  instead  of  performing  the  experiment  in  the  Order  of  Action 

T  .,      T      ,1  -,  ,11     of  Amboceptor 

manner  described,  the  process  is  reversed  so  that  andcompie- 
the  corpuscles  are  first  treated  with  the  solution 
of  complement  and  then  with  the  amboceptors,  the 
corpuscles  are  not  hemolyzed.  During  the  wash- 
ing process  the  complement  is  entirely  separated 
from  the  cells,  and  from  this  fact  it  is  clear  that 
direct  union  between  corpuscle  and  complement 
does  not  occur;  only  sensitized  cells  take  up  com- 
plement. 

The  question  as  to  whether  the  corpuscles  in 
taking  up  amboceptors  do  so  by  chemical  combina- 


ment. 


14G 


IX FECI! 0\  AM)  IMMIXITY. 


Cytophilous 
Haptophore 
of  the  Am- 
boceptor. 


The  Absorption 
Experiment 
in  the  Cold. 


tion  or  by  physical  absorption  has  been  contended 
with  some  vigor.  Elirlicli  believes  tliat  the  process 
is  one  of  chemical  nnion,  and  if  one  adheres  to  this 
view  it  becomes  necessary  to  assign  binding  or 
haptophorous  groups  both  to  the  red  blood  cells 
and  to  the  amboceptors.  In  contrast  to  another 
haptophore  which  the  amboceptor  possesses  and 
which  will  be  described  below,  that  one  which 
unites  with  the  cell  is  called  the  cytophilous  hapto- 
phore. The  haptophore  of  the  erythrocyte  which 
enters  into  the  union  is  an  essential  part  of  a  re- 
ceptor of  the  red  cell,  consequently  we  say  that  tlie 
amboceptor  unites  with  a  receptor  of  the  corpuscle. 

The  heating  of  serum  to  56°  C.  provides  one 
means  of  apparent  isolation  of  the  amboceptor 
from  the  complement,  but  this  is  not  a  true  isola- 
tion in  that  complement  is  merely  rendered  inac- 
tive by  the  heat  rather  than  totally  eliminated. 

Ehrlich  and  Morgenroth  devised  a  method  liy 
which  the  amboceptors  may  be  separated  from  a 
fresh  immune  serum  without  in  any  way  injuring 
the  complement.  This  is  accomplished  by  per- 
forming the  binding  experiment,  already  alluded 
to,  at  a  low  temperature.  The  serum,  containing 
both  amboceptors  and  complement,  is  cooled  to  0° 
C.  or  slightly  above,  by  means  of  a  freezing  mix- 
ture of  salt  and  ice.  A  suspension  of  the  homolo- 
gous corpuscles  is  cooled  to  the  same  point,  the 
serum  is  added  and  the  mixture  maintained  at  0° 
to  4°  C.  for  fifteen  to  twenty  minutes.  At  the 
end  of  this  time  the  sensitized  cells  are  removed 
bv  immediate  centrifugation  at  a  low  temperature, 
and  are  washed  entirely  free  from  serum  by  the 
use  of  ice-cold  salt  solution.  If  the  low  tempera- 
ture has  been  adhered  to  rifforouslv  and  the  w^ork 


UNION  WITH  CELLS.  147 

done  quickly,  the  corpuscles  are  not  laked  during 
the  manipulations  in  spite  of  the  presence  of  both 
amboceptors  and  complement.  Furthermore,  the 
washed  sensitized  cells  remain  intact  even  when 
their  temperature  reaches  that  of  the  thermostat, 
whereas  if  some  fresh  normal  serum  or  the  serum 
from  which  the  amboceptors  were  absorbed  is 
added,  they  undergo  hemolysis  as  readily  as  when 
treated  with  the  active  immune  serum.  The 
original  immune  serum  is  now  a  solution  of  com- 
plement, and  fresh  corpuscles  which  are  added  to 
it  are  not  dissolved  because  of  the  absence  of  ambo- 
ceptors. 

These  results  show  the  following  important 
facts :  Amboceptor  and  complement  exist  side  by 
side  in  an  immune  serum,  not  as  a  united  sub- 
stance. Union  of  amboceptor  with  cell  is  inde- 
pendent of  complement,  the  latter  being  taken  up 
only  after  the  amboceptor-cell  reaction  has  oc- 
curred. Amboceptors  unite  with  cells  at  a  low 
temperature,  whereas  complement  requires  a 
higher  temperature  for  its  union  and  for  the  fer- 
ment-like activity  by  which  it  dissolves  or  kills  the 
cells. 

That    constituent    of    the    amboceptor    which  compfemento- 
unites  with  the  cell  has  been  referred  to  as  the  phore  of  Am-** 
cytophilous  haptophore.     Ehrlich  and  his  follow-  •'*•"'»**»'■• 
ers  believe  that  complement  in  establishing  con- 
nection with  the  cells  does  so  by  combining  with  a 
second  haptophore  of  the  amboceptor,  after  the 
latter  has  sensitized  the  er>i;hrocyte  or  bacterium. 
Hence,  an  amboceptor  has,  as  the  name  implies, 
two  receiving  groups  or  haptophores,  the  second 
being  the  complement ophilous  haptophore    (Fig. 
7).     It  is  hardlv  desirable  to  discuss  various  ex- 


Amboceptors 


148  lyFECTlOX  A\D  LMMIXITY. 

periments  which  I'urnisli  additional  evidence  of  the 
amboceptor  nature  of  the  therniostabile  body.  The 
observed  phenomena  allow  one  to  assign  to  it  the 
two  liaptophores  mentioned. 
Action  of  There  is  a  conflict  of  ideas  as  to  the  nature  of 
the  change  produced  b)^  the  amboceptors,  as  a  re- 
sult of  which  the  cells  are  made  susceptible  to  the 
action  of  complement.  Bordet  speaks  of  the  am- 
boceptor as  the  substance  sensibilisatrice,  the  sen- 
sitizing substance;  and  his  conception  of  the  ac- 
tion of  the  two  substances  he  has  compared  rough- 
ly to  the  opening  of  a  lock  for  which  two  keys  are 
demanded.  One  key,  amboceptor,  is  needed  to 
prepare  the  lock  for-  the  action  of  the  second  key, 
complement,  the  latter  being  the  one  which  really 
opens  it. 

Metchnikoff  applies  the  name  fixator  to  the 
therniostabile  body,  having  in  mind  the  action  of 
a  mordant  in  preparing  tissues  or  other  substances 
for  the  reception  of  a  dye;  this  differs  little  from 
preparator,  the  word  used  by  Gruber. 

The  idea  of  Ehrlich,  however,  is  distinctly  at 
variance  with  the  conceptions  mentioned,  for  he 
sees  in  the  union  of  amboceptor  with  cell  nothing 
more  than  the  introduction  of  a  new  chemical 
affinity,  i.  e.,  one  which  attracts  complement,  and 
this  new  affinity  does  not  lie  in  the  cell  itself,  but 
rather  in  the  amboceptor  (complementophilons 
haptophore)  after  the  union  has  occurred.  Hence, 
the  terms  intermediary  body  {Zwisclienkorper) , 
copula  of  Milller,  and  desmon  of  London,  are 
words  which  carry  with  them  the  meaning  that  the 
amboceptor  first  unites  with  the  cell  and  then  acts 
as  a  linking  substance  through  which  complement 
finally  is  put  in  relation  to  the  cell.    This  also  is 


COMPLEMENTOID.  149 

the  meaning  embodied  in  the  amboceptor  of 
Ehrlich,  the  word  indicating  more  accurately  his 
conception  of  the  method  by  which  the  substance 
acts  as  an  intermediary  body. 

If  we  consider  it  established  that  in  the  process  structure  of 
of  cytolysis  union  occurs  between  complement  and  ""*  *"'^"  " 
amboceptor  we  must  at  the  same  time  assign  a 
haptophorous  group  to  complement.  Union  would 
be  impossible  without  it.  Corroborative  proof  of 
the  existence  of  this  haptophore  lies  in  the  fact 
that  immunization  with  complement  results  in  the 
formation  of  anticomplement,  a  prerequisite  for 
which  is  union  of  complement  with  cell  receptors 
in  the  immunized  animal ;  and  this  union,  it  seems 
necessary  to  assume,  takes  place  through  a  binding 
group.  The  mere  possession  of  a  haptophore,  how- 
ever, does  not  account  for  the  ferment-like  activity 
of  complement.  The  latter  characteristic  resides 
in  the  so-called  zymotoxic  group;  hence,  comple- 
ment, having  a  binding  and  a  toxic  group,  has  a 
structure  like  that  of  a  toxin. 

Somewhat  loosely  we  have  said  that  the  inactiv-  Compiemen- 
ity  of  a  serum  which  has  been  heated  to  56°  C. 
depends  on  destruction  of  the  complement.  This 
is  not  strictly  true,  however,  for  such  treatment 
destroys  only  the  zymotoxic  group,  the  haptophor- 
ous constituent  remaining  uninjured.  Comple- 
ment altered  in  this  respect  is  called  complemen- 
toid,  and  it  is  analogous  to  toxoid,  agglutinoid  and 
precipitoid.  Two  essential  facts  go  to  show  that 
this  is  the  principle  change  wrought  b}^  heating. 
First,  the  fact  stated  above,  that  immunization 
with  complementoid,  causes  the  formation  of 
anticomplement.  Second,  complementoid  may 
exceed    true   complement   in   its    affinity   for   the 


Amboceptors. 


150  ISFKVTIOy  AyO  IMMUNITY. 

amboceptor,  and  if  sensitized  cells  are  treated  with 
a  serum  containing  a  mixture  of  complement  and 
complementoid,  the  latter  may  occupy  completely 
the  complementophilous  haptophores  of  the  ambo- 
ceptors and  thus  may  block  the  way  for  action  on 
the  part  of  complement.  This  is  again  the  spe- 
cific inhibition  which  has  been  mentioned  in  con- 
nection with  toxoids,  agglutinoids  and  precipi- 
toids.  This  is  the  Complementoid-Verstopfung  of 
Ehrlich. 
formationof  Tho  amboceptor,  as  the  characteristic  property 
of  a  bactericidal  or  of  a  hemolytic  serum,  is  a  spe- 
cific product  of  the  immunization,  whereas  the 
amount  and  character  of  complement  in  the  im- 
munized animal  undergoes  little  or  no  change. 
We  are,  of  course,  obliged  to  consider  the  ambo- 
ceptors as  a  product  of  the  cells  of  the  body.  In 
the  terminology  of  Ehrlich,  they  are  discarded  cell 
receptors,  and  with  their  two  haptophores  repre- 
sent a  more  complex  structure  than  either  the  re- 
ceptors of  antitoxin  or  agglutinin ;  the  latter  are 
uniceptors;  the  former  amboceptors,  and  because 
of  their  higher  differentiation  Ehrlich  has  called 
them  receptors  of  the  third  order  (Fig.  7). 

Wlien  micro-organisms  gain  entrance  to  the 
body  they  are  killed  and  dissolved  in  considerable 
masses.  As  a  result  of  the  solution,  certain  bac- 
terial constituents  reach  the  circulation,  and 
among  them  are  molecules  or  receptors  which  pos- 
sess haptophores  capable  of  uniting  with  a  par- 
ticular type  of  amboceptor,  the  latter  being  an  in- 
tegral part  of  some  tissue  cells.  This  union  hav- 
ing taken  place,  an  affinity  for  circulating  com- 
plement may  be  created  as  in  the  test-tube  experi- 
ments.    We  have  thus  the  possibility  of  stimula- 


FORMATION   OF  AMBOCEPTORS.  151 

tion  of  the  cell  by  the  bacterial  constituent  itself 
as  a  toxic  or  unusual  food  substance,  or  the  toxic 
action  may  be  caused  by  products  of  disintegra- 
tion of  the  bacterial  substance,  the  disintegration 
having  been  accomplished  by  the  digestive  action 


Fig.  7. — Graphic  representation  of  receptors  of  the  third 
order,  and  of  some  substance  uniting  with  one  of  them. 
c.  Cell  receptor  the  third  order,  an  amboceptor ;  e^  one  of  the 
haptophores  of  the  amboceptor,  with  which  some  food  sub- 
stance or  product  of  bacterial  disintegration,  f,  may  unite  ; 
g,  the  other  haptophore  of  the  amboceptor  with  which  com- 
plement may  unite  ;  K,  complement ;  li,  the  haptophore,  and 
!s,  the  zymotoxic  group  of  complement.  From  Ehrlich's 
"Schlussbetrachtungen,"  Nothnagel's  System  of  Medicine, 
vol.  viii. 

of  the  complement  which  was  taken  up  by  the  am- 
boceptor. The  effect  is  that  of  an  unusual  stimu- 
lation, in  response  to  which  the  cell,  if  not  fatally 
injured,  reproduces  many  amboceptors  correspond- 
ing to  the  type  which  was  occupied  or  injured.  As 
in  the   formation   of   other   antibodies,  the  new- 


151 


IXFKCTIOS    A\D  /.l/.l/r.V/7'I'. 


Specificity  of 
Bactericidal 
Amboceptors 
and  Comple- 
ments. 


Bacterial 
Receptors. 


foniicil  ;iinlioco]iti"iTs  riMcli  tlu^  iiriicral  llniils  of  llio 

( "iiiiri'i'iiiiiL;'  till'  s|)('rillrit\'  of  sci'uiii-licmolysin? 
ami  >i'ruiii-li;iclci'iolysin!^  for  llicii-  liomolo,u"ous 
cells,  wo,  of  course,  refer  to  tlic  spocifieitv  of  the 
wliolo  nniboceptor-comploinoiit  ooniplox.  Tt  is  noc- 
cssarv  to  tlirow  tlio  rpsponsibilitv  on  both  sub- 
staiicos.  l)eeiUise  of  tlio  variations  wliicli  exist 
amono^  complements  as  well  as  amons;  ambocep- 
tors. Tnasmnch,  however,  as  the  heat-resistant 
body  alone  is  increased  dni'in.u'  iinmnnization  or 
infection,  the  a'l'eater  ]y,\vi  of  the  sj^ecifieiiy  wonld 
seem  to  depend  on  the  nature  of  the  ainhoceplor 
rather  than  on  that  of  complement. 

.Ml  bacteria  which  stimulate  to  the  formation 
of  bactericidal  serums  do  so  because  of  certain  re- 
ceptors which  they  possess.  These  are,  of  course, 
analoofous  to  the  receptors  of  erythroc}i;eR  which 
cause  the  production  of  the  hemolytic  bodies  in 
serum.  Bacteria  have,  in  addition,  many  otliei-  re- 
ceptors, some  of  which  cause  the  development  of 
ao-glutinins.  In  the  latter  instance  we  speak  of  the 
agglutinogenic  receptors  of  the  cells,  but  there  is 
no  name  of  equal  eonvenience  which  is  used  to 
designate  the  receptors  which  stimulate  to  the 
formation  of  amboceptors.  No  two  micro-organ- 
isms contain  an  identical  receptor  apparatus :  if 
the  contrary  were  the  case  their  antiserums  wonld 
coincide  in  their  bactericidal  action.  Therefore,  the 
cell  receptors  (amboceptors)  with  wdiich  they  nnite 
during  immnnization  differ  correspondinglv  in 
their  c^i;ophilous  haptophores.  The  c\i:ophilous 
haptonhore  of  the  typhoid  amboceptor  finds  its 
specific  counterpart  in  the  tvphoid  bacillus,  and 
finding  no  such  counterpart  in  the  vibrio  of  chol- 


Complements. 


COMPLEMENT   AND    ANTWOMPLEMENT     153 

era,  the  latter  can  not  be  sensitized  by  the  anti- 
typhoid serum;  on  this  fact  depends  the  specificity 
of  the  serum.  This  conception  does  not  interfere 
with  the  explanation  of  the  group  reaction  among 
bactericidal  serums,  for  it  is  conceivable  that  the 
colon  bacillus,  for  example,  has,  in  addition  to 
those  receptors  which  characterize  the  organism,  a 
small  percentage  of  receptors  which  are  identical 
with  those  characterizing  the  typhoid  bacillus.  In 
accordance  with  this  possibility  an  antityphoid 
serum  may  well,  as  it  does,  show  some  increased 
bactericidal  power  'for  closely  related  organisms. 
Hence  the  explanation  of  group  bacteriolysis  is 
identical  with  that  of  group  agglutination. 

There  is  a  wide  difference  of  opinion  regarding  Multiplicity  of 
the  unity  of  complement,  or  alexin,  its  S3Tionym. 
Bordet  and  his  followers  stand  for  the  unity  of  the 
alexins,  and  their  position  rests  on  the  fact  that  a 
given  normal  serum  may  be  used  to  activate  many 
different  amboceptors.  We  should  appreciate  that 
this  phenomenon  might  depend  on  the  broad  range 
of  action  of  a  single  complement,  or  on  the  pres- 
ence of  different  complements  each  being  specific 
for  a  particiilar  amboceptor.  Ehrlich  and  his 
school  take  the  latter  view  and  have  actually  dem- 
onstrated a  multiplicity  of  complements  in  a  few 
instances.  Ehrlich  and  Sachs  treated  fresh  nor- 
■mal  serums  (complement)  in  various  ways,  such 
as  digestion  with  papain,  partial  destruction  with 
alkalies,  heat,  etc..  and  were  able  by  these  methods 
to  destroy  the  complement  for  one  kind  of  ambo- 
ceptor, while  the  serum  still  retained  its  power  for 
activating  other  amboceptors.  Accordingly,  it 
seems  clear  that  the  ability  of  a  normal  serum  to 
activate  a  given  amboceptor  depends  not  only  on 


1.5-1  I\FECT10.\   A.\D   IMMl  .MTY 

'  the  presence  of  complement  in  a  ^iciiLTal  sense,  but 
on  the  presence  of  a  suitable  complement,  1.  e.,  one 
the  haptophore  of  Avhicli  corresponds  to  the  com- 
plementophilous  haptophore  of  tlie  amboceptor. 
This  point  is  of  great  importance  in  reference  to 
the  treatment  of  infectious  diseases  with  antibac- 
terial serums,  for  the  efficacy  of  the  serum  would 
seem  to  depend  on  the  introduction  of  suitable 
complement  in  conjunction  with  the  amboceptors, 
or  on  the  existence  of  such  complement  in  the  l)ody 
of  the  patient. 
Anticom-  Added  proof  of  the  multiplicity  of  complements 
lias  been  obtained  by  experiments  with  anticom- 
plements.  As  stated,  the  latter  are  obtained  by 
immunization  of  suitable  animals  with  normal  or 
immune  serums  which  contain  complement  or  com- 
plementoid.  When  they  are  mixed  with  the  liomolo- 
gous  complements  the  haptophores  of  the  latter 
are  bound  by  means  of  the  haptophores  of  the  anti- 
complements.  The  evidence  of  this  union  lies  in 
the  fact  that  a  complement  which  has  been  treated 
with  its  specific  anticomplement  is  no  longer  able 
to  activate  the  appropriate  amboceptor.  With 
properly  selected  serums,  it  may  be  shown  that  a 
given  anticomplement  will  neutralize  a  comple- 
ment which  is  specific  for  one  amboceptor,  but  will 
have  no  effect  on  another  complement  which  acti- 
vates a  different  amboceptor.  Hence,  complements 
differ  at  least  in  this  respect  that  not  all  have  iden- 
tical haptophores.  Immunization  with  leucocytes, 
ceils  which  contain  complement,  also  causes  the 
formation  of  anticomplement.  Both  natural  and 
acquired  antibacterial  immunity  may  be  lowered 
by  the  injection  of  anticomplement  which  is  ho- 
mologous to  the  complement  of  the  animal. 


POLYCEPTORS. 


155 


Some  time  ago  Ehrlich  expressed  the  opinion 
that  an  amboceptor  in  certain  cases  may  have  more 
than  one  complementophilous  haptophore;  in 
other  words,  that  it  may  be  a  polyceptor  rather 


Fig.  8. — Illustrating  the  amboceptor  with  more  than  one 
complementophilous  haptophore  (a  polyceptor).  a.  Cell  re- 
ceptor ;  l)j  cytophilous  haptophore  of  the  amboceptor  ;  c,  the 
dominant  complement ;  d,  the  non-dominant  complements 
oc ,  The  haptophore  of  the  amboceptor  for  the  dominant  com- 
plement; /3,  those  for  the  non-dominant  complements.  (From 
Ehrlich  and  Marshall.) 

than  an  amboceptor.  This  has  again  been  empha- 
sized recently  by  way  of  explaining  the  ability  of 
an  amboceptor  to  absorb  from  a  normal  serum  not 
only  the  complement  which  serves  to  activate  the 


l.-it;  INFECTION  AND  IMMUNITY. 

■  amboceptor,  but  also  others  whieli  ]iapi)eii  to  be 
present  in  the  serum.  The  former  is  spoken  of  as 
tlie  dominant  complement  and  the  latter  as  non- 
dominant  complements.  Figure  8  is  an  illustra- 
tion of  such  a  polyceptor. 
Antiam-        Tf  oue  immunizes  with  an  immune  scrum  the 

boceptors.  n       j.   •  i  j    •  i  x* 

]no(luct  is  spoken  of  m  a  general  wa)^  as  an  anti- 
immune  serum.  The  latter  contains,  as  stated, 
anticomplement,  and  through  the  agency  of  this 
substance  the  antiserum  antagonizes  the  action  of 
the  serum  which  was  used  for  the  immunization. 
Inasmuch,  however,  as  the  immune  serum  contains 
amboceptors  also,  the  antagonistic  action  of  the 
antiserum  may  depend,  in  part,  on  the  presence  of 
antiamboceptors.  DifTerentiation  between  the  ac- 
tion of  anticomplement  and  antiamboceptor  is  dif- 
ficult, but  it  may  be  accomplished  in  certain  cases 
by  appropriate  binding  experiments.  Serum  1,  an 
inactive  hemoh^ic  serum,  i.  e.,  a  solution  of  ambo- 
ceptors and  complementoid,  is  treated  with  serum 
2.  Serum  2  has  been  obtained  by  irhmunization  of 
an  animal  with  serum  1,  and  contains  anticomple- 
ment and  possibly  antiamboceptors.  If  serum  2 
contains  only  anticomplement,  it  will  have  no  ef- 
fect on  the  amboceptors  of  serum  1,  when  the  two 
are  mixed.  The  amboceptors  are  free  to  sensitize 
corpuscles  which  may  be  added,  and  the  latter  when 
sensitized  undergo  hemolysis  in  the  presence  of 
complement.  Tf,  however,  serum  2  contains  anti- 
amboceptors, either  the  C3iophilous  or  the  comple- 
raentophilous  haptophore  of  the  amboceptor  will 
be  bound.  In  either  case  corpuscles  which  are 
added  subsequently  would  not  appear  as  sensitized, 
for  if  the  cytophilous  haptophore  had  been  bound 
by  antiamboceptor  union  between  cell  receptor  and 


DIVERSION  OF  COMPLEMENT.  157 

amboceptor  could  not  occur;  and  if  the  comple- 
inentophilous  liaptophore  had  been  preoccupied 
complement  would  have  no  effect  even  if  the  ambo- 
ceptors had  united  with  the  cells  by  their  unbound 
cytophilous  haptophores.  Ehrlich  and  Morgenroth 
demonstrated  such  antiamboceptors  for  certain 
hemolytic  serums,  and  it  was  their  belief  that  they 
combine  with  the  cytophilous  rather  than  with  the 
complementophilous  haptophore  of  the  ambo- 
ceptor. However,  Ehrlich  has  recently  been  able 
to  prove  the  occurrence  of  an  antibody  for  the  com- 
plementophilous haptophore  in  one  case.  Pfeiffer 
also  reports  the  demonstration  of  antiamboceptors  Danger  of 
for  the  specific  amboceptors  of  anticholera  serum,  of  Antiam- 
The  possibility  of  antianiboceptor  formation  is  one  **""  °^^' 
of  practical  bearing,  in  view  of  the  fact  that  the 
prolonged  treatment  of  a  patient  with  a  bacteri- 
cidal serum  may  result  in  the  development  of  such 
antibodies.  If  present  in  sufficient  amount  they 
would  combine  with  new  amboceptors  which  were 
injected  and  thus  deviate  the  latter  from  the  bac- 
teria. 

A  phenomenon  equally  of  theoretical  and  prac-   Diversion  of 
tical  importance  has  to  do  with  the  so-called  diver-  and  it's  Theo- 
sion   (Ahlenkv/ng)    of  complement.     It  has  been  reticai Danger. 
found  that  the  action  of  a  bactericidal  or  hemoMic 
serum  is  lessened,  if  a  great  excess  of  amboceptors* 
over  complement  is  added.    To  explain  this  fact 
ISTeisser  and  Wechsberg  have  supposed  that  when 
so  many  amboceptors  are  present  that  all  can  not 
be  taken  up  by  the  cells,  those  which  remain  free 
are  able  to  combine  with  some  of  the  complement 
which  is  present  and  thus  prevent  the  accession  of 
the  latter  to  the  sensitized  cells ;  that  is  to  say,  the 
complement  is  diverted  from  its  natural  course  of 


15S  IXFECTlOy  AXD  IM.UUMTY. 

aetiou  (Fig.  9).  This  amounts  to  a  protection  of 
the  sensitized  cells  from  the  action  of  the  comple- 
ment. The  phenomenon  led  Wechsberg  to  sug- 
gest that  in  the  therapeutic  administration  of  bac- 
tericidal serums  it  may  be  possible  to  give  too 
mucli  of  the  serum.  Although  diversion  of  com- 
plement is  a  demonstrated  fact,  its  importance  in 
serum  thera])v  is  perhaps  not  definitely  settled. 
Hemolytic  Am-  It  is  of  interest  that  amboceptors  are  widely  dis- 
""^^"venom.  tributcd  in  the  animal  kingdom,  and  that  in  cer- 
tain instances  they  may  be  demonstrated  in  the 
secretions.     It   has    lone;    l)een    Icnown    that    the 


Fig.  9. — Illustrating  diversion  of  complement.  The  free 
amboceptors  have  combined  with  the  available  complement, 
and  thereby  prevented  the  latter  from  activating  the  am- 
boceptors which  have  united  with  the  bacterial  cell.  (From 
Neisser  and  Wechsberg.) 

venoms  of  serpents  owe  a  great  deal  of  their  tox- 
icity to  their  power  of  destroying  red  blood  cells.* 
A  given  venom  may  contain  several  toxic  sub- 
stances, and  the  poisons  of  different  serpents  by 
no  means  coincide  in  their  toxic  properties.  Cobra 
venom  has  at  least  two  distinct  toxins,  one  for  the 
nervous  tissue  and  one  which  dissolves  erythro- 
cytes, the  neurotoxin  having  the  greater  patho- 
genic significance;  it,  moreover,  agglutinates  red 
blood  corpuscles.  The  venom  of  the  rattlesnake, 
on  the  other  hand,  is  neurotoxic  to  a  less  degree, 
but  has  a  pronounced  influence  in  causing  capil- 

*  See  also  part  IT,  Chapter  Z.  concerning  venoms. 


ENDOGOMPLEMENT.  159 

lary  hemorrhages.  The  latter  power  Flexner  as- 
cribes to  a  toxin  for  endothelial  cells,  which  he 
calls  hemorrhagin.  Through  the  works  both  of 
Flexner  and  Koguchi  and  of  Kyes,  facts  were 
learned  concerning  the  hemolytic  toxin  of  cobra 
venom,  which  may  be  of  great  importance  in  prob- 
lems of  general  immimity.  It  seems  that  the 
hemolysin  of  venom  is  an  amboceptor  rather  than 
a  toxin  of  the  usual  nature,  and  that  the  aid  of 
complement  is  necessary  for  its  toxic  action.  The 
venom  itself  contains  only  the  amboceptors,  hence 
the  toxicity  of  the  substance  depends  on  its  being 
complemented  after  it  is  introduced  into  the  body. 
The  possession  of  suitable  complement,  therefore, 
is  a  source  of  danger  in  this  instance  rather 
than  a  means  of  protection  for  the  individual. 
One  may  very  well  suspect  that  a  similar  relation- 
ship is  possible  in  connection  with  other  sub- 
stances which  are  as  yet  unknown. 

A  fact  of  additional  importance  is  that  the  am-  Endocom- 
boceptor  finds  suitable  complement  not  only  in  the 
serum  of  the  animal  but  it  may  also  be  activated 
by  a  complement  which  the  erythrocytes  them- 
selves contain.  Kyes  speaks  of  the  latter  as  endo- 
complement,  i.  e.,  endocellular  complement. 

In  attempting  to  discover  the  nature  of  the  com-  Lecithin. 
plement  which  is  present  in  the  erythrocytes,  vari- 
ous substances  existing  normally  in  the  red  cells, 
as  cholestrin  and  lecithin,  were  obtained  in  pure 
form  and  their  activating  power  for  the  cobra  am- 
boceptors was  tested  in  reagent-glass  experiments. 
From  this  work  it  was  learned  that  lecithin,  a  defi- 
nitely known  chemical  substance,  has  the  activat- 
ing power,  and  it  was,  therefore,  assumed  that  the 
endocomplement  of  er}i;hrocytes  is  nothing  more 


IGO 


IXFECTIOX  AXD  IllMUyiTY 


Cobra-lecithid. 


Hemolysis  by 

the  Combined 

Action  of 

Colloids. 


or  less  than  lecithin.  All  erythrocytes  contain 
lecithin,  yet  not  all  are  equally  susceptible  to  the 
action  of  venom  in  the  absence  of  serum  comple- 
ment ;  that  is  to  say,  endocellular  lecithin  does  not 
act  as  complement  with  equal  readiness  in  all 
cases.  In  order  to  explain  this  variation  it  was 
necessary  to  assume  that  the  lecithin  in  the  cells 
of  one  animal  may  be  more  available  as  comple- 
ment because  it  is  bound  to  other  cell  constit^^ents 
only  in  a  very  loose  way,  whereas  in  more  resistant 
cells  the  union  is  of  a  firmer  nature. 

The  relationship  between  cobra  amboceptors  and 
lecithin  seems  to  be  a  very  definite  one,  for  Kyes 
was  able  to  obtain  a  union  of  the  two  without  the 
intervention  of  erythrocytes.  The  resulting  sub- 
stance, the  cobra-lecithid  of  Kyes,  is  a  completed 
toxin  and  needs  no  further  activation.  We  have 
yet  to  learn  of  the  true  nature  of  this  new  cofti- 
pound,  the  discovery  of  which  seemed  to  augur  a 
more  intimate  chemical  laiowledge  of  the  sub- 
stances which  are  concerned  in  immunity. 

Lecithin  is  a  colloid,  and  in  this  connection  it  is 
interesting  to  note  that  it  may  be  used  in  combina- 
tion with  still  another  colloid  in  such  manner  that 
the  hemolysis  which  they  cause  is  analogous  to 
that  produced  by  hemol^iic  amboceptors  and  com-^ 
plements.  Landsteiner  tried  the  effect  of  col- 
loidal silicic  acid  on  erythrocytes  which  were  en- 
tirely freed  from  serum,  with  the  result  that  the 
corpuscles  were  agglutinated  under  its  influence. 
It  developed  further,  however,  that  colloidal  silicic 
acid  not  only  acts  as  an  agglutinin,  but  also  simu- 
lates a  hemol}i;ic  amboceptor,  and  in  the  latter 
capacity  it  may  be  activated  either  by  the  ordinary 
complement  of  serum  or  b}^  lecithin.     Hence,  we 


ACTION    OF   8ALT8.  161 

have  here  an  instance  of  the  entire  cytolytic  action 
being  performed  by  two  known  chemicals,  which 
in  their  action  appear  to  be  analogous  to  ambocep- 
tors and  complements.  Yet  even  the  action  of 
these  substances  is  obscure,  for  although  the  chem- 
ical formulae  of  silicic  acid  and  lecithin  are  suffi- 
ciently well  known,  the  explanation  of  their  activ- 
ity as  colloids  is  equally  obscure  with  that  of  the 
albuminous  substances. 

Another  recent  discovery  which  tends  to'  bring  Neutralization 
the  immune  substances  into  closer  touch  with  pure  by  saTts.**"*"* 
chemistry  is  that  of  Hektoen  concerning  the  abil- 
ity of  certain  salts  (calcium  chlorid,  barium 
chlorid,  etc.),  to  combine  with  complement  in 
such  a  way  that  the  latter  loses  its  activating  and 
combining  function  in  relation  to  amboceptors. 
This  was  mentioned  incidentally  under  the  sub- 
ject of  antitoxins.  The  activity  of  the  comple- 
ment is  again  restored  if  the  inhibiting  salts  are 
precipitated  by  suitable  chemicals.  The  salts  are 
used  in  such  dilutions  that  they  are  largely  ionized, 
and  Manwaring  believes  their  inhibiting  action  is 
due  to  the  formation  of  compounds  of  the  posi- 
tive ions  with  the  complement,  resulting  in  such 
substances  as  Ca-complement,  Ba-complement, 
IHlg.  When  the  precipitating  chemicals  are  added 
the  ions  are  freed  from  this  combination,  as  a  re- 
sult of  which  the  complement  recovers  its  activat- 
ing properties.  It  has  not  as  yet  been  determined 
whether  variations  in  the  salts  in  the  fluids  of  the 
body  cause  changes  in  resistance  by  their  action  on 
native  complements. 


CHAPTER  XIII. 


Cytotoxin  or 
Cytolysin. 


Theoretical 

Utility  of 

Cytotoxins. 


CYTOTOXICS. 

Following  the  discovery  of  immune  hemolytic 
serums  it  was  a  short  step  to  experiments  which 
involved  immunization  with  various  other  tissue 
cells,  and  as  a  result  of  such  work  we  are  to-day 
familiar  with  antiserums  for  almost  every  organ 
of  the  body. 

Metclmikoff  gave  tlie  name  of  cytotoxins  to  those 
serums  which  destroy  cells  other  tlum  bacteria 
and  erythrocytes;  the  word  cytolysin  is  used  syn- 
onymously. jSTaturally  a  serum  which  destroys  any 
cell  whatsoever  is  cytotoxic,  but  according  to  the 
rather  loose  custom  which  prevails,  we  speak  of 
bacteriolysans,  hemolysins  and  other  cytolysins,  in- 
cluding among  the  latter  serums  which  destroy 
leucocytes,  the  cells  of  the  liver,  Iridney  and  other 
organs. 

Cytotoxins  are  of  interest,  not  only  because  they 
are  produced  in  accordance  with  the  general 
laws  of  anti-body  formation,  l3ut  they  have,  in  ad- 
dition, a  certain  theoretical  and  perhaps  practical 
importance.  Immediately  on  their  discovery  the 
possibility  became  manifest  that  they  might  be 
utilized  in  the  elucidation  of  certain  physiologic 
and  pathologic  problems.  For  example,  by  put- 
ting the  thyroid  out  of  function  through  in- 
jections of  thyrotoxic  serum  it  might  be  pos- 
sible to  confirm,  or  to  prove  incorrect,  cer- 
tain theories  as  to  the  role  of  the  gland  in 
metabolism.  Or,  by  the  selective  destruction  of  a 
tissue,   facts  concerning  its   regenerative   powers 


SPECIFICITY.  103 

might  be  learned.  The  use  of  an  antipancreatic 
serum  might  throw  some  light  on  the  nature  of 
diabetes.  Therapeutic  possibilities  also  suggested 
themselves.  One  might  be  able  by  means  of  artifi- 
cial anticytotoxic  serums  to  counteract  cy  to  toxins 
which  were  being  formed  pathologically  in  the 
body.  Or,  by  injecting  small  amounts  of  a  cyto- 
toxin,  perhaps  one  could  stimulate  to  a  renewed 
production  of  the  homologous  cells ;  small  doses  of 
a  hemolytic  serum  might  be  useful  in  combating 
anemias.  Or  small  amounts  of  leucotoxic  serum 
might  caiise  an  increase  in  the  number  of  leuco- 
cytes, and  thereby  an  increased  resistance  to  infec- 
tion. Perhaps  autocytotoxins  are  formed  in  some 
such  manner  as  the  following:  An  extraneous 
toxic  substance  causes  the  destruction  of  a  few 
kidney  cells,  the  constituents  of  the  latter  reach 
the  circulation  and  stimulate  other  organs  to  the 
formation  of  autonephrotoxic  amboceptors,  which 
then  assist  in  the  destruction  of  more  renal  tissue, 
with  the  result  that  a  vicious  cycle  is  set  up. 

In  spite  of  so  many  theoretical  values,  the  study  Lack  of 
of  cytotoxic  serums  has  not  yielded  the  results 
which  were  anticipated,  perhaps  chiefly  because  of 
their  lack  of  specificity  (Pearce  and  others).  Al- 
though the  cells  of  the  different  organs  differ  wide- 
ly in  their  morphology  and  function,  there  are  no 
doubt  certain  chemical  constituents  (receptors) 
which  they  possess  in  common.  Of  this  we  have 
experimental  proof  from  the  fact  that  immuniza- 
tion with  one  type  of  cell  yields  a  serum  which  is 
toxic  for  the  cells  of  various  organs.  It  is  difficult 
or  impossible  to  injure  one  organ  to  the  exclusion 
of  all  others  by  means  of  a  cytotoxin.  One  may 
'attempt  to  purify  a  C}^otoxic  serum  through  ab- 


Specificity. 


1(54  1XFECTI0^'  AND  IMMUNITY. 

sorption  of  the  adventitious  amboceptors  by  means 
of  the  corresponding  cells.  Inasmuch,  however,  as 
the  result  is  a  decrease  in  the  chief  amboceptors 
as  well  as  of  the  adventitious,  the  desired  object  is 
not  fully  realized.  Theoretically  the  cytotoxic 
treatment  of  malignant  tumors  offers  an  impor- 
tant field  for  research.  But  here,  too,  various  dif- 
ficulties are  involved,  as  lack  of  specificity  of 
scrums  and  the  multiplicity  of  cell-types  which 
constitute  different  tumors. 

Determination  Experiments  with  cytotoxic  serums  may  be  con- 
'^ActTofu  ducted  in  vitro  or  in  the  living  animal.  In  either 
ease  a  necessary  condition  for  the  recognition  of 
the  cytotoxic  action  is  the  presence  of  some  dis- 
tinctive sign  of  vitality  on  the  part  of  the  cell,  the 
loss  of  which  may  be  taken  as  evidence  of  cell- 
death.  Loss  of  motility  and  of  proliferative  power 
indicate  the  death  of  bacteria,  and  solution  of 
hemoglobin  the  death  of  erythrocytes.  Under  par- 
ticular conditions  loss  of  motility  on  the  part  of 
certain  tissue  cells,  as  spermatozoa,  leucoc}i:es  and 
ciliated  epithelium,  is  an  evidence  of  cell  death  or 
cell  injury.  The  toxic  action  of  serums  on  cells  of 
fixed  form  is  more  difficult  to  determine,  and  for 
evidence  one  must  rely  on  such  points  as  clearing 
of  the  protoplasm  (digestion?),  swelling  of  the 
cell  and  nucleus,  actual  solution  of  the  C3d:oplasm, 
or  degenerations  of  the  homologous  organs  when 
the  serum  is  injected  into  the  living  animal. 
Technicof       The  tcchnic  of  immunization  with  tissue  cells  is 

Immunization,  g^^^^]^^  ^q  that  of  immunization  with  bacteria.  In 
order  to  obtain  leucocytes  in  abundance,  artificial 
leucoc}i;osis  is  produced  in  the  peritoneal  or  pleural 
cavity   by   the   injection   of   bouillon,    or    lymph 


AMBOCEPTORS   AND    COMPLEMENTH.        1G5 

glands,  spleen  or  bone-marrow  may  bo  ground  up 
and  injected. 

Immunization  with  solid  organs,  as  liver,  kidney 
or  testicle,  is  easily  accomplished,  a  necessary  pre- 
liminary for  injection  being  a  thorough  disintegra- 
tion of  the  tissue  by  grinding  with  sterile  sand ; 
the  resulting  mass  when  suspended  in  salt  solution 
passes  through  the  injecting  needle  readily. 

Cytotoxins,  like  bacteriolysins  and  hemolysins,  Amboceptors, 
are  complex  substances,  in  that  they  consist  of  am-  and  AiftTcyto^ 
boceptors    and    complements.     The    amboceptors  to"'"*- 
alone  are  increased  during  immunization,  the  com- 
plement being  a  normal  constitu.ent  of  the  serum 
of  the  animal.     The  phenomena  of  inactivation 
and  reactivation  are  observable  here  as  in  connec- 
tion with  other  cytolytic  serums.     Anticytotoxins 
are  readily  produced  by  immunization  with  many 
cytotoxins;  the  antiserum  usually  consists  of  anti- 
complement,  but  in  some  instances  antiambocep- 
tors  have  been  described. 

Simultaneously,  or  nearly  so,  Landsteiner  in  spermotoxin. 
Vienna  and  Metchnikoff  in  Paris  reported  the 
production  of  spermotoxic  serums  by  immuniza- 
tion with  spermatozoa,  the  natural  motility  of 
which  rendered  the  recognition  of  cell  death  easy. 
The  technie  which  Landsteiner  first  employed  was 
that  of  the  Pfeiffer  experiment  in  that  he  immun- 
ized guinea-pigs  with  the  spermatozoa  of  cattle  and 
observed  loss  of  motility  on  the  part  of  the  cells 
when  they  were  injected  into  the  peritoneal  cavity 
of  the  immunized  animals.  Comparable  with 
many  other  cytotoxins,  spermotoxin  kills  the  ho- 
mologous cell  without  causing  its  solution.  The 
loss  of  motility  i&  also  observed  in  hanging-drop 
preparations  provided  a  fresh  or  a  complemented 


100  lyFECTioy  axd  immuxity. 

seriini  is  used.  Most  normal  serums  show  a 
greater  or  less  degree  of  toxic  action  for  the  sper- 
matozoa of  other  animals,  and  normal  spermotox- 
ins  like  the  immune  consist  of  amboceptor  and 
complement.  Orotclmikoff  claims  to  have  pro- 
duced an  autospermotoxin  by  immunizing  guinea- 
pigs  with  the  spermatozoa  of  other  guinea-pigs. 

TVlien  a  spermotoxic  serum  is  injected  into  the 
living  animal  it  is  thought  that  the  amboceptors 
are  taken  up  by  the  homologous  cells,  and  this 
■would  seem  to  affect  the  vitality  of  the  sperma- 
tozoa, inasmuch  as  De  Leslie  rendered  male  mice 
sterile  for  16  to  20  days  by  the  injection  of  the 
serum. 

It  is  of  theoretical  interest  that  castrated  ani- 
mals will  yield  spermotoxin  by  immunization, 
showing  that  the  amboceptors  are  not  of  necessity 
produced  by  the  analogous  tiissue  of  the  immun- 
ized animal.  From  the  fact  that  spermotoxic 
serums  are  hemolytic,  it  is  assumed  that  certain 
receptors  are  common  to  erA-throc;\i:es  and  sperma- 
tozoa. Hemol}i;ic  serums,  on  the  other  hand,  may 
not  be  spermotoxic.  There  is  nothing  contradic- 
tory in  this  lack  of  reciprocal  action,  for  those  re- 
ceptors which  are  common  to  the  two  cells  may  not 
be  important  for  the  life  of  the  spermatozoon, 
whereas  the  oppo'site  condition  prevails  with  the 
erythrocyte. 

It  is  certainly  of  interest  that  immunization  with 
the  plasma  of  ova  causes  the  formation  of  spermo- 
toxic amboceptors,  a  fact  which  points  to  certain 
common  constituents  of  the  two  cells. 

Antispermotoxin  may  be  produced  by  immimiza- 
tion  with  spermotoxic  serum  (anticomplement  or 
antiamboceptor). 


LEUCOTOXIC    SERUM.  167 

Pollowinsr  technic  similar  to  that  employed  by  Cytotoxin 

T         -,    .    •  -r^  1  i.    •        1  i    J.       •       'O""  Ciliated 

Landstemer,  von  Dungern  obtained  a  cytotoxic  Epithelium. 
serum  for  ciliated  epithelium  of  the  trachea.  The 
cells  disintegrated  in  the  peritoneal  cavity  of  the 
immunized  animal,  but  not  in  that  of  the  normal 
animal.  This  serum  also  proved  to  be  hemolytic 
in  spite  of  the  fact  that  no  erythrocytes  were  in- 
cluded in  the  injections.  That  the  receptors  which 
characterize  ciliated  epithelium  are  widely  distrib- 
uted is  shown  by  the  fact  that  immunization  with 
cow's  milk  causes  the  formation  of  a  cytolytic 
serum  for  the  tracheal  epithelium  of  the  cow. 

Leucotoxic,  lymphotoxic  or  lymphatotoxic  Leucotoxin. 
serums  are  prepared  by  immunization  with  ex- 
udates which  are  rich  in  leucocytes,  or  with  the 
emulsions  of  lymphoid  organs:  lymph  glands, 
spleen,  bone  marrow.  Metchnikoff  prepared  the 
first  serum  of  this  nature  by  the  injection  of  the 
spleen  of  rats  into  guinea-pigs.  Leucotoxic  serums 
are  toxic,  not  only  for  leucocytes,  but  also  for  red 
corpuscles  and  endothelial  cells.  When  injected 
into  the  peritoneal  cavity  the  endothelium  is 
thrown  off,  and  when  given  subcutaneously  the 
capillary  endothelium  is  attacked,  with  the  result 
that  blood  escapes  to  form  a  large  hematoma.  The 
action  of  the  serum  on  leucoc}i;es  may  be  observed 
in  vitro.  The  mononuclear  cell's  are  often  more 
susceptible  than  the  polymorphonuclears,  although 
this  depends  somewhat  on  the  animals  and  the 
particular  organ  used  for  immunization.  The  cells 
lose  their  motilit3%  the  cytoplasm  becomes  trans- 
parent, and  swells  to  form  a  large  clear  vesicle, 
which  appears  to  be  surrounded  by  a  sharp,  thin 
membrane.  The  cell  contents  may  be  discharged 
or  entirely  liquefied,  the  nucleus  alone  being  rec- 


1G8 


INFECTIOX  AXD  IMMUNITY. 


Old  Age. 


Effect  of  Leu- 
coto\ic  Serum 
on  Resistance 
to  Infections. 


ognizable.  Leucocytes  are  agghitinated  by  the 
serum.  A  strong  lencotoxic  serum  may  be  fatal 
to  the  animal  when  injected  into  the  peritoneal 
cavity  or  blood  stream,  the  exact  cause  of  death 
being  obscure. 

]\Ietchnikoff,,  taking  the  view  that  the  phenom- 
ena of  old  age  depend  on  the  destruction  of  vari- 
ous tissue  cells  by  the  mononuclear  leucocytes 
(macrophages),  expressed  the  hope  that  a  lympho- 
toxic  serum  might  be  utilized  to  combat  the  action 
of  these  cells  with  the  result  that  life  would  be 
prolonged.  Wliether  or  not  his  view  as  to  the 
cause  of  old  age  is  correct,  his  plan  of  antagonizing 
it  had  to  be  abandoned  because  leucotoxic  serums 
do  not  injure  the  macrophages  to  the  exclusion  of 
other  leucoc}i;es. 

The  injection  of  a  leucotoxic  serum  into  the  per- 
itoneal cavity  of  a  guinea-pig  causes  a  temporary 
decrease  in  the  number  of  leucoc}i;es,  and  during 
this  period  of  MqDoleucocytosis  the  resistance  of  the 
animal  to  peritoneal  infections  with  the  organisms 
of  typhoid  and  cholera  is  lowered.  One  may  refer 
this  effect  to  the  destructive  action  of  the  serum 
on  the  leucocytes,  by  which  phagocytosis  is  pre- 
vented, or,  according  to  Wassermann,  it  may  de- 
pend on  the  action  of  anticomplement  which  the 
leucotoxic  serum  contains.  (Leucocj'tes  contain 
complement,  hence  immunization  with  leucoc3rtes 
causes  the  formation  of  anticomplement.)  It  is 
probable  that  both  factors  are  of  influence.  In  the 
course  of  24  to  48  hours  after  peritoneal  injection 
of  the  serum,  the  leucocytes  reaccumulate  to  an 
enormous  extent.  During  this  secondary  hyper- 
lencocytosis  resistance  to  peritoneal  cholera  or 
tj-phoid  is  increased.     Some  non-toxic  substances. 


Serum. 


NEPHROTOXIN    AND    NEPHRITIS.  1G9 

as  bouillon,  have  a  similar  effect,  and  although  the 
secondary  leucocytosis  is  never  so  great  as  that 
caused  by  the  leucotoxic  serum,  the  protective  ac- 
tion is  equally  high.  It  would  seem  that,  leucoc3d;e 
for  leucocyte,  those  which  accumulate  following 
the  injection  of  leucocytoxie  serum  are  less  efficient 
in  antibacterial  action  than  those  whose  presence 
is  caused  by  nontoxic  substances.  (Eicketts.) 
Hence  there  probably  is  no  field  for  leucotoxic 
serum  as  a  means  of  temporarily  increasing  resist- 
ance to  bacterial  infections. 

By  guarded  immunization  Besredka  obtained  an 
antileucotoxic  serum. 

Nephrotoxic  serums  have  been  brought  into  Nephrotoxic 
close  relationship  with  clinical  and  anatomic  prob- 
lems by  a  number  of  investigators.  Some  normal 
serums  are  held  to  be  nephrotoxic  inasmuch  as 
their  injection  is  followed  by  albuminuria  and 
renal  degenerations.  Immune  nephrotoxins  have 
a  similar  but  more  pronounced  effect,  and  Linde- 
man  referred  the 'death  of  his  experiment  animals 
to  the  development  of  a  uremic  condition.  Of 
more  than  ordinary  interest  is  the  claim  of  cer- 
tain workers  that  autonephrotoxins  may  be  formed 
in  the  body.  One  (Lindeman)  caused  a  toxic 
nephritis  in  dogs  by  the  injection  of  potassium-  Autenephro- 
bichromate.  The  serum  of  this  dog,  although  free 
from  chromic  acid,  was  toxic  for  other  dogs,  pro- 
ducing the  symptoms  which  are  caused  by  an  im- 
mune nephrotoxic  serum.  It  was  supposed  that 
the  chromic  acid  in  the  fir'st  dog  caused  disintegra- 
tion of  renal  cells  and  that  the  constituents  of  the 
latter  were  then  taken  up  by  nephrotoxic  receptors 
which  normally  reside  in  the  organs  of  the  ani- 
mal; as  a  result  the  receptors  were  overproduced 


170  INFECTIOy  AXD  IMMUMTY. 

and  their  presence  became  manifest  when  the 
serum  was  injected  into  other  dogs.  In  accord- 
ance with  this  view  the  original  toxic  cause  of  a 
degenerative  nepliritis  would  be  of  less  conse- 
quence for  the  continuance  of  the  condition  than 
the  formation  of  the  nephrotoxic  amboceptors ;  i.  e., 
the  formation  of  an  autonephrotoxin. 

Somewhat  similar  results  were  obtained  by  oth- 
ers through  ligation  of  the  renal  vein  or  artery  on 
one  side.  Constituents  of  cells  of  the  isolated  kid- 
ney were  supposed  to  be  absorbed,  and  as  a  conse- 
quence nephrotoxic  amboceptors  were  produced  in 
excess  by  organs  of  uncertain  identity.  To  the 
action  of  the  new-formed  bodies  were  attributed 
the  degenerative  changes  which  were  found  in  the 
opposite  kidney,  and  the  nephrotoxic  properties 
which  the  serum  manifeested  when  injected  into  a 
healthy  animal  of  the  same  species. 
Antinephro-  Accordiug  to  Ascoli  and  Figari  unilateral  neph- 
Hypertropin^  rectomy  so  injures  the  opposite  kidney  (overwork) 
that  the  serum  of  the  animal  becomes  nephrotoxic. 
They  state  also  that  an  animal,  the  serum  of  which 
contains  nephrotoxin,  may  antagonize  the  latter 
by  the  production  of  antinephrotoxin,  and  suggest 
that  spontaneous  recovery  from  nephritis  may  be 
due  to  the  action  of  such  an  antibody.  They  would 
account  for  the  cardiac  hypertrophy  of  nephritis 
by  the  action  of  nephrotoxic  serum  in  causing  con- 
traction of  the  peripheral  vessels  with  consequent 
increase  of  blood  pressure;  and  for  the  nervous 
s>Tnptoms  on  the  basis  that  the  serum  contains  a 
neurotoxic  constituent. 

We  liardly  dare  consider  such  far-reaching  con- 
clusions as  decisive  until  they  have  been  extensively 
confirmed.    Yet  whatever  mav  be  their  real  value 


HEPATO-    AND    NEUROTOXINS. 


171 


Neurotoxin. 


they  serve  to  emphasize  the  possibility  that  those 
principles  which  are  so  important  in  relation  to 
immunity  against  infectious  diseases,  may  be 
equally  important  in  relation  to  other  pathologic 
conditions. 

Hepatotoxins  have  been  obtained  by  a  number  Hepatotoxins. 
of  workers,  and  the  attempt  has  been  made  to  pro- 
duce autohepato toxins  by  injecting  liver  tissue  of 
the  guinea-pig  into  animals  of  the  same  species. 
The  success  was  not  unqualified.  Hepatotoxins 
when  injected  are  reported  to  cause  insular  degen- 
erations of  the  liver ;  however,  the  lesions  may  be 
caused,  in  part  at  least,  by  capillary  emboli  of  en- 
dothelial cells  or  erythrocytes. 

Neurotoxic  serums  have  been  studied  with  some 
thoroughness.  Whether  one  injects  the  cerebrum, 
cerebellum  or  spinal  cord,  the  resulting  serums 
apparently  are  similar;  either  an  anticerebral  or 
an  anticerebellar  serum  will  cause  degenerations 
of  the  spinal  ganglion  cells.  In  view  of  their 
broad  range  of  action  it  seems  improbable  that 
neurotoxic  serums  will  be  of  service  in  clearing  up 
the  etiology  of  system  degenerations  of  the  nervou's 
tracts.  They  are  usually  hemolytic  and  hemag- 
glutinating  and  may  also  be  endotheliotoxic  and 
leucotoxie.  Wlien  mixed  with  emulsions  of  the 
homologous  brain  tissue  the  neurotoxic  ambocep- 
tors are  bound  by  the  receptors  of  the  nervous  tis- 
sue, and  the  serum  consequently  loses  its  toxicity. 
Antineurotoxic  serums  have  been  described. 

Syncytdolysin  is  the  name  given  to  a  serum  which 
is  obtained  by  immunization  with  the  placenta. 
Certain  writers  (Veit  and  Scliolten,  Charrin  and 
Delamare)  report  that  the  injection  of  placentar 
tissue  alone  causes   albuminuria,  a  consideration 


Cyncytiotoxin 
in  Relation  to 
Eclampsia. 


172  IXFKCTIOX  AMI  IMMUXITY. 

\\iiieli  led  thorn  to  assume  tliat  the  phieentar  cells 
contain  a  nephrotoxic  substance.  Inasmuch  as 
]ilacentar  cells  or  their  constituents  may  reach  the 
circulation  during  eclampsia  (Schmorl)  it  was 
not  a  long  step  to  suppose  that  the  nephritis  of 
pregnancy  is  due  to  the  toxic  sync}i:ial  cells  which 
are  absorbed.  The  results  which  Weichardt  re- 
ported gave  some  strength  to  the  view  just  cited. 
By  treating  placentar  tissue  of  rahbits  with  the 
specific  cyncytiolysin  the  toxin  supposedly  was  lib- 
erated, and  the  mass  when  injected  into  normal 
rabbits  is  said  to  have  produced  symptoms  of  an 
eclamptic  nature.  On  the  basis  of  these  observa- 
tions the  hope  has  been  expressed  that  an  anti- 
toxin for  eclampsia  might  be  prepared  by  immun- 
ization with  placentar  tissue.  However,  the  con- 
ditions are  by  no  means  simple;  any  value  which 
the  destruction  of  circulating  syncytial  cells  or 
their  toxin  would  afford  might  be  more  than  offset 
by  the  action  of  the  hemotoxin  and  neurotoxin 
which  the  serum  is  said  to  contain.  Wliether  or 
not  the  hypothetical  toxin  of  syncytial  cells  may 
be  separated  from  the  other  cell  constituents,  and 
whether  immunization  with  the  toxin  will  yield 
an  antitoxic  serum  are  possibilities  which  remain 
for  further  investigation ;  the  results  cited  have 
not  been  obtained  by  all  observers. 

Liepmann  hopes  for  a  serum-diagnosis  of  preg- 
nancy. If,  as  supposed,  the  blood  of  a  pregnant 
woman  contains  syncitial  cells  or  their  products 
of  degeneration,  the  serum  when  mixed  with 
a  specific  syncytiolysin  may  cause  a  precipitate. 
He  claims  to  have  demonstrated  the  presence  of 
placentar  constituents  in  the  circulation  by  this 
biolocjic  method. 


TEYRO-,    FA'NCREOTOXrN,    ETC. 


173 


Thyrotoxin. 


Antithyroid  serum  is  prepared  by  jinrniinjza- 
tion  with  ground-up  thyroid  tissue  or  with  extracts 
of  the  organ.  It  is  hemolytic,  even  though  all  the 
blood  has  been  washed  from  the  tissue  which  was 
injected.  Portis  immunized  with  the  "colloid" 
material  of  the  gland  obtaining  a  hemolytic  thyro- 
toxic serum.  When  injected  into  the  living  animal 
degenerative  changes  are  produced  in  the  thyroid, 
and  some  authors  report  the  tetanic  phenomena 
Avhich  often  follow  surgical  removal  of  the  thyroid. 
In  very  careful  work,  however,  Portis  could  not 
produce  "the  exact  picture  presented  by  thyrodec- 
tomized  animals."  Degenerative  changes  were 
foimd  in  various  organs,  as  liver,  spleen  and  kid- 
neys. 

Brown  Pusey  has  made  the  interesting  sugges- 
tion in  regard  to  sympathetic  ophthalmia  that  the 
disease  may  be  due  to  the  formation  of  autocyto- 
toxins  which  are  specific  for  the  cells  of  the  inner 
surface  of  the  ciliary  body  and  iris.  The  disinte- 
gration products  of  the  corresponding  cells  in  the 
eye  which  was  primarily  injured  would  constitute 
the  stimulus  to  the  formation  of  the  specific  anti- 
bodies. The  possibility  is  as  yet  a  problematic 
one. 

The  experimental  study  of  cytotoxic  serums  for 
the  pancreas  has,  up  to  the  present  time,  thro"nm 
little  light  on  pancreatic  diseases.  It  stated  that 
the  serum  may  cause  transient  glycosuria,  and  it 
is  said  to  have  an  antitryptic  action  in  experiments 
performed  in  the  test -glass. 

The  results  of  different  observers  concerning  the  other 
action  of  antiserums  for  the  adrenal  gland  are  not 
in  entire  accord.     Although  degenerative  changes 
may  be  caused  in  the  gland  when  the  serum  is  in- 


Sympathetic 
Ophthalmia. 


Pancreotoxin. 


Cytotoxins. 


174 


IM'ECTIOX  AXD  IlIilUyiTY. 


Toxin  of 
Exhaustion. 


Concerning 
Autocytotoxins. 


"Horror 
Autotoxicus." 


jected,  the  action  is  not  specific;  the  serum  may 
be  highly  hemolytic  (Abbott). 

Ceni  claims  to  have  demonstrated  in  the  circula- 
tion of  epileptics  a  cytotoxin  which  causes  tlie  ep- 
ileptic attacks,  and  reports  the  production  of  a 
specific  antitoxin. 

Weichardt  has  published  descriptions  of  a  toxin 
which  is  peculiar  to  states  of  exhaustion,  giving 
an  account  of  the  specific  antitoxin  which  he  pro- 
duced by  immunization. 

Other  c}^otoxins  which  have  been  prepared,  as 
those  for  the  pituitary  body,  gastric  mucosa  and 
cardiac  muscle,  have  at  the  present  time  nothing 
more  than  general  biological  interest. 

It  would  seem  that  no  question  in  relation  to 
CA-totoxic  serums  is  more  important  than  the  pos- 
sil^ility  that  autoc^-totoxins  may  develop  and  in- 
stitute the  vicious  cycle  which  was  mentioned  ear- 
lier. It  is  true  that  the  results  of  some  investiga- 
tors suggest  the  probability  of  such  a  process,  but 
it  would  be  going  too  far  to  say  that  its  existence 
as  an  important  pathologic  law  has  been  estab- 
lished. On  the  contrary,  the  development  of  auto- 
cytotoxins  is  one  of  the  rarest  of  occurrences  in 
experimental  work;  and  Ehrlich  has  spoken  of 
the  inability  of  the  body  to  form  such  antibodies 
as  a  condition  of  ^^lorror  autotoxicus."  The  cells 
of  our  Iddneys  and  our  erythrocytes  certainly  do 
degenerate,  and  it  is  quite  possible  that  the  recep- 
tors which  are  thereby  liberated  actually  reach 
cytotoxic  amboceptors  which  are  situated  in  other 
organs.  In  the  event  that  the  process  extends  to 
this  point.  Ehrlich  assumes  that  the  amboceptors 
are  of  a  sessile  nature,  that  in  spite  of  the  stimula- 
tion to  which  the  cells  are  subjected  the  "sessile 


% 

"HOIiROn  AU'rOTOXINS."  175 

amboceptors"  may  not  be  overprodiicofl  aiifl  lib- 
erated as  in  the  case  of  antibodies  for  bacterial 
substances  or  for  the  cells  of  other  species.  In 
accordance  with  this  explanation  we  are  saved 
from  intoxications  of  the  nature  in  question  be- 
cause of  the  sessile  nature  of  the  cytotoxic  ambo- 
ceptors. 


CHAPTER  XIV. 


PHAGOCYTOSIS. 

As  one  ma}'  learn  from  the  writings  of  Metchni- 
koff.  phagocytosis,  in  its  broad  sense,  exercises 
three  distinct  functions:  nutritional,  resorptive 
and  protective. 
Phagocytosis  Phagoc}i;osis,  for  purposes^  of  nutrition,  is  most 
ofNuTntlon!  highly  developed  in  unicellular  ameboid  organ- 
isms, but  is  found  also  in  animals  of  considerable 
organic  differentiation.  It  is,  perhaps,  nowhere 
more  strildng  than  among  certain  myxomycetes, 
which  are  large,  naked,  multinucleated,  protoplas- 
mic masses  belonging  to  the  plant  kingdom,  and 
which  possess  a  peculiar,  slow,  undulating  motility. 
Ingestion  is  accomplished  through  protoplasmic 
arms  (pseudopodia)  which  are  thro  "mi  out  to  en- 
velop tlie  object.  Minute  plant  and  animal  cells, 
living  or  dead,  are  ingested  in  this  manner  by  the 
myxomycetes,  amebse  and  other  unicellular  organ- 
isms and  are  subsequently  digested  by  means  of 
intracellular  ferments.  The  ferments  which  have 
been  extracted  from  such  cells  are  proteohiic  since 
they  digest  gelatin  and  fibrin,  usually  in  an  acid 
but  sometimes  in  an  alkaline  medium;  that  from 
amebae  has  been  called  amibodiastase.  In  the  proc- 
ess of  digestion  a  "vacuole,"  acid  in  reaction  and 
containing  the  ferment,  forms  around  the  in- 
gested particle.  -In  certain  phagoc^^tic  unicellular 
organisms  the  protoplasm  shows  a  degree  of  differ- 
entiation, a  mouth  and  an  anus  being  simulated  at 
points  where  the  food  is  most  readily  taken  in  and 
discharged.    Instances  are  cited  in  which  ameboid 


0EEM0TAXI8. 


177 


organisms  protect  themselves  against  inimical  cells 
by  ingesting,  killing,  ami  finally  discharging  or 
digesting  the  latter. 

The  botanist,  Pfeiffcr,  first  described  the  phe- 
nomena of  negative  and  positive  chemotaxis  in  re- 
lation to  the  myxomycetes.  Under  certain  condi- 
tions they  either  are  attracted  toward  or  move 
from  moist  places.  That  a  negative  chemotaxis 
may  be  changed  into  a  positive  was  shown  in  rela- 
tion to  salt  solutions.  Wlien  placed  in  the  vicinity 
of  or  in  contact  with  strong  solutions  the  cell  re- 
cedes, whereas  if  one  passes  gradually  from  weaker 
to  stronger  solutions  the  latter  eventually  attract 
rather  than  repel  the  cell. 

As  one  goes  higher  in  the  animal  scale  intracel- 
lular digestion  for  purposes  of  nutrition  is  con- 
fined to  rather  definite  groups  of  cells.  The  intes- 
tinal epithelium  of  certain  invertebrates  consists 
of  "sessile  phagocytes,"  cells  Avhich.  individually 
or  after  fusion  into  plasmodial  masses,  surround 
and  digest  solid  particles  of  food.  It  is  said  that 
in  sponges  the  digestive  tract  is  not  sharply  sepa- 
rated from  the  mesodermal  tissue,  and  the  cells  of 
the  latter  share  with  the  former  the  function  of 
intracellular  digestion. 

In  higher  invertebrates  and  in  all  vertebrates 
the  intestinal  epithelium  ceases  to  be  essentially 
phagocytic,  digestion  being  accomplished  rather  by 
ferments  which  have  been  secreted  hy  the  intestinal 
and  related  glandular  epithelium.  Such  animals, 
nevertheless,  possess  an  abundance  of  phagoc3'tic 
cells,  but  they  are  in  the  main  mesoblastic  in  na- 
ture, and  may  have  nothing  more  than  a  remote 
relationship  to  the  nutrition  of  the  organism. 


Chemotaxis. 


Intestinal 
Phagocytes. 


ITS  INFECTION  AND  IMMUNITY. 

Macrophages       Metclmikoll'  divides  tlie  pliao-ocvtic  cells  of  ver- 

and  Micro-  .  '        ^      • 

phages,  tebrates  mto  the  macrophages  and  the  micro- 
phages.  Tlie  macrophages  or  hirge  phagocytes  in- 
clude the  large  lymphocytes,  endothelial  cells, 
ameboid  connective  tissue  cells  and  others  which 
may  occasionally  take  up  foreign  particles.  Our 
polymorphonuclear  leucoc}d;es  are  the  micro- 
phages.  In  relation  to  immunity  we  are  concerned 
chiefly  with  the  large  lymphoc5d;es  (macrophages), 
and  the  polymorphonuclear  leucocytes  (micro- 
phages).  Although  such  cells  may  contain  many 
ferments,  Metchnikoff  recognizes  but  one  type  in 
Cytases.  relation  to  their  resorptive,  digestive  and  bacteri- 
cidal activities.  This  he  calls  CAi:ase  and  distin- 
giiishes  that  of  the  macrophage  as  macrocytase  and 
that  of  the  microphage  as  microcytase.  Cytase 
corresponds  to  the  complement  of  Ehrlich.  The 
two  cells  do  not  have  identical  activities,  the  ma- 
crophage being  concerned  specially  in  the  resorp- 
tion of  tissue  cells  and  in  immunity  to  certain 
chronic  diseases,  as  tuberculosis  and  leprosy, 
whereas  the  microphage  is  the  cell  which  is  con- 
spicuously antimicrobic  in  relation  to  acute  infec- 
tions. 
Resorption  of  According  to  Metchnikoff,  the  leucoc;vtes  are 
very  active  in  the  resorption  of  useless  or  foreign 
cells.  During  the  metamorphosis  of  certain  in- 
vertebrates it  is  said  that  the  larval  tissues  are 
englobed  and  digested  by  wandering  pha- 
goc}i;ic  cells.  In  involution  of  the  uterus 
the  muscular  tissue  is  invaded  by  leuco- 
CA-tes  which  take  up  and  digest  or  carry  away  the 
"retrogressive  elements."  Metchnikoff's  concep- 
tion   of   certain    atrophic    processes,    particularly 


Native  Cells. 


A TROPni  C   PROCEHHEH. 


179 


those  which  are  grouped  among  the  senile  atro- 
phies, is  of  interest  to  pathologists.  In  sclerotic 
atrophy  of  the  ovaries  the  large  lymphocytes  in- 
vade the  tissue,  surround  and  destroy  the  ova  and 
follicular  epithelium  and  eventually,  as  fibroblasts, 
participate  in  the  formation  of  fibrous  tissue  which 
to  a  degree  is  substituted  for  the  original  struc- 
ture. In  old  individuals  or  in  those  of  failing 
mentality  it  is  said  that  ganglionic  cells  are  found 
in  a  greater  or  less  degree  of  atrophy  because  of 
the  action  of  certain  mononuclear  phagocytes 
(neuronophages)  which  are  contiguous  to  or  form 
a  zone  around  the  cell.  The  neuronophages  may 
represent  mononuclear  cells  from  the  blood  or 
those  of  proliferated  neurogliar  tissue.  The  best 
examj)les  of  this  condition  were  found  in  very  old 
dogs.  The  chromophores  of  the  skin,  according  to 
Metchnikoff,  may  be  considered  as  chromophages. 
Wliether  or  not  they  are  of  epithelial  origin,  as  he 
claims,  they  are  said  to  exist  normally  in  the  hairs 
in  a  latent  or  inactive  condition.  As  old  age  comes 
on,  or  as  a  result  of  other  obscure  causes,  their 
attitude  becomes  an  active  one,  and  they  proceed 
to  take  up  and  digest  the  normal  pigments  of  the 
hairs.  Hence,  white  hairs  are  the  result  of  an 
autoparasitism  by  certain  mononuclear  phago- 
cytes. In  muscular  atrophy  it  is  held  that  the 
sarcoplasm  takes  up  the  striated  tissue  after  the 
manner  of  phagocytes. 

We  come  into  closer  touch  with  our  general  sub- 
ject of  immunity  when  we  consider  the  resorptive 
function  of  the  phagocytes  for  cells  which  are  for- 
eign to  the  host,  for  example,  toward  erythrocytes 
which  are  injected  for  the  purpose  of  producing  a 


The  Whitening 
of  Hairs. 


Resorption  of 
Foreign  Cells. 


Formation  of 
Cytotoxins. 


180  IXFECTIOy  A^D  IMMUNITY. 

liemolytic  serum.  Followiug  such  an  injection  into 
the  peritoneal  cavity  there  occurs  a  great  accession 
of  macropliages  which  ingest  the  erythrocytes,  dis- 
solve the  hemoglohin  and  eventually  digest  the 
stroma.  The  same  phagocytes  are  involved  in  the 
resorption  of  any  other  foreign  cells  of  animal  ori- 
gin vrhich  may  be  injected.  In  view  of  the  intracel- 
lular lieraolysis  by  the  leucocytes,  one  may  suspect 
that  the  latter  contain  a  hemolytic  ferment;  one 
which,  perhaps,  is  analogous  to  the  hemolysin 
(hemoh-tic  amboceptors  and  complement)  of 
serums.  On  this  point  there  has  been  sharp  dis- 
cussion. Metchnikoif  cites  observations  to  show 
that  a  ferment  of  this  nature  may  be  extracted 
from  the  lymphoid  organs,  that  it  contains  a  heat- 
susceptible  constituent,  and  that  when  fresh  it 
may  be  used  to  reactivate  a  heated  hemolytic 
serum.  This  would  indicate  that  the  leucocytes 
contain  cytase  (complement),  but  it  is  not  clear 
that  they  would  also  contain  the  fixators  (ambo- 
ceptors). Nevertheless,  the  demonstration  of  an 
intraleucoc}i;ic  hemolysin  and  a  Icnowledge  of  the 
phagocytic  power  of  the  leucocytes  for  erythro- 
cytes form  the  basis  for  Metchnikoff's  belief  that 
serum-hemolysin  is  nothing  more  than  intraleuco- 
C3i;ic  hemolysin,  which  under  proper  conditions 
may  reach  the  serum  or  plasma.  By  an  extension 
of  this  conception  it  is  held  that  all  cytolysins  are 
produced  by  the  macrophages. 
Thermostabiie  Korschim  and  Morgenroth,  on  the  other  hand, 
Organ^E^xTracts!  ol)tained  from  lymphoid  and  various  other  organs, 
not  a  therraolabile  hemolysin,  but  one  which  with- 
stands prolonged  boiling — a  coctostabile  hemolysin 
which  is  soluble  in  alcohol,  shows  no  amboceptor- 


CYTAHE.  181 

complement  composition,  and  is  incapable  of  yield- 
ing antihemolysin  by  immunization.  These  re- 
sults, Metchnikoff  holds,  are  only  in  apparent  dis- 
cord with  those  obtained  by  himself  and  his  pu- 
pils, and  depend  on  the  methods  of  extraction 
wliich  were  employed.  In  order  to  obtain  the  ther- 
molabile  hemolysin  uncontaminated  with  the  ther- 
mostabile,  the  extraction  must  be  a  rapid  one.  If, 
on  the  other  hand,  it  is  prolonged,  as  Metchnikoff 
assumes  that  of  Korschun  and  Morgenroth  to  have 
been,  the  intracellular  ferments  digest  the  remain- 
ing cell  constituents,  including  the  thermolabile 
hemolysin,  and  the  thermostabile  hemolysin  is  lib- 
erated or  formed  in  the  process. 

Believing  that'cytase,  under  normal  conditions, 
exists  only  within  the  leucocytes,  and  that  its  pres- 
ence outside  these  cells  is  artificial,  Metchnikoff 
cites  experiments  similar  to  the  following  in  sup- 
port of  his  views : 

Given  a  guinea-pig  which  has  been  immunized  cytasean 
with  the  blood  of  a  goose :  if  fresh  goose  corpuscles  substancef 
are  injected  into  the  peritoneal  cavity,  the  cells  are 
hemolyzed  in  the  fluid  without  the  occurrence  of 
phagocytosis.     Two  explanations  of  the  extraleu- 
cocytic  presence  of  cjrfcase  and  fixators,  which  is  in- 
dicated by  this  result,  are  possible :  first,  that  they 
are  present  normally  and  continuously  in  the  plas- 
ma of  the  immunized  animal,  or,  second,  that  they 
become  liberated  at  the  time  the  corpuscles  are  in- 
jected. According  to  Metchnikoff,  the  latter  conten- 
tion prevails  rather  than  the  former.  He  recognizes  phagoiysis. 
a  phenomena  which  bears  the  name  of  phagol^^sis, 
i.  e.,  solution,  partial  or  complete,  or  phagocj'tes. 
Almost  anv  foreign  substance  or  fluid  which  one 


IS-2 


IXFKCTloy  AM)  IMMIXITY. 


Liberation  of  niny  clioosc  to  ]nit  iu  coiitact  witli  leucocytes  so 
pVa*g*'oiysi^8^.  stimulates  or  injures  them  that  they  discharge  cer- 
tain of  their  constituents.  If  the  fixators  and 
cytase  are  among  the  constituents  which  are  dis- 
cho.rged  at  the  time  the  injection  is  made,  the 
extracellular  hemolysis  encountered  in  the  experi- 
ment described  above  might  depend  on  the  libera- 
tion of  these  substances  rather  than  on  their  nat- 

Preventionof  ural  occurrcnce  in  the  plasma.  If  this  be  true, 
aao  ysis.  _^^^^|  ^^  ^^^^  could  in  some  way  fortify  the  leucoc^^es 
against  phagolysis,  the  plasma  would  remain  free 
from  hemolytic  power.  ]\Ietchnikoff  accomplishes 
such  fortification,  i.  e.,  prevents  phagolysis,  by  a 
simple  procedure,  which  demands  nothing  more 
than  the  peritoneal  injection  of  a  small  quantity 
of  bouillon  or  salt  solution  twentj^-four  hours  in 
advance  of  the  experiment.  Possibly  by  this 
means  the  leucocytes  have  been  habituated  to  the 
presence  of  a  foreign  fluid,  or  the  neAV  leucocytes 
which  accumulate  possess  greater  resistance.  What- 
ever the  explanation,  the  erythrocytes  which  are 
injected  at  this  critical  time  are  said  not  to  un- 
dergo extracellular  hemolysis,  but  instead  are  en- 
globed  and  dissolved  by  the  macrophages.  These 
results  and  others  of  a  similar  nature  are  the  basis 
for  the  belief  that  cytase  normally  is  intracellular, 
and  that  it  becomes  extracellular  only  when  the 
leucocytes  are  subjected  to  injurious  influences. 
The  fact  that  the  serum  of  detibrinated  or  coagu- 
lated blood  contains  cytase  is  not  in  discord  Avith 
such  an  opinion,  for  in  this  instance  also  the  leu- 
cocytes may  be  injured  to  such  a  degree  that  cer- 
tain of  their  constituents  are  discharged.  We  are 
well  aware  that  fibrin-ferment  is  liberated  under 
these  circumstances. 


NATURAL   IMMUNITY.  183 

It  was  equally  desirable,  if  possible,  to  determine  Fixators 
the  relation  of  fixators  to  the  leucocytes.  The  sit-  Leucocytes.'' 
nation  is,  however,  very  complex,  and,  although 
Metchnikoff  regards  the  fixators  as  secretion  or  ex- 
cretion products  of  phagocytic  cells,  the  question 
is,  perhaps,  not  definitely  settled.  When  phagoly- 
sis  is  prevented  in  the  manner  described,  the  in- 
jected erythrocytes  may  well  absorb  fixators  from 
the  plasma  and  still  undergo  no  hemolysis  until  en- 
globed  by  the  phagocytes.  It  is  considered  that 
fixators  in  contrast  to  cytase  may  exist  in  the  cir- 
culating plasma. 

Phagocytosis  as  a  feature  of  local  resistance  phagocytosis 
against  microbic  invasion  was  considered  in  rela-  '" '"""""'ty- 
tion  to  inflammation.  We  come  now  to  speak  of 
the  relationship  of  the  leucocytes  to  general 
states  of  immunity,  having  reference  .to  the  condi- 
tions which  have  been  designated  as  natural  and 
acquired  antibacterial  immunity,  and  natural  and 
acquired  antitoxic  immunity. 

The  first  expressions  of  Metchnikoff  concerning 
the  antimicrobic  activity  of  phagocytes,  the  power 
of  freeing  the  organism  from  "invaders  of  every 
sort,"  were  made  altogether  from  an  a  priori  stand- 
point in  an  address  delivered  in  1883,  "TJeber  die 
Heilkraf  fce  des  Organismus."  He  justified  his  po- 
sition on  general  grounds,  having  in  mind  the 
"more  general  phenomena  of  phagocytosis  and  the 
resorption  of  corpuscular  elements,"  as  he  had 
observed  them  in  various  zoological  studies. 

Shortly  there  came  to  him  the  opportunity  of   NaturaMmmun- 
studying  an  infectious  disease  among  the  Daphnia 
(water-flea),  a  small  transparent  crustacean.   The 
disease  was  caused  by  a  blastom3'Ces  which  forms 


ity  to  Bacteria. 


1S4  iXFEcrioy  and  immunity. 

a  long  neeclle-shapod  spore.  After  being  swal- 
lowed by  the  animal  the  spores  penetrate  the  in- 
testinal wall  into  the  body  cavity  where  they  are 
snrrounded,  englobed  and  digested  by  the  white 
blood  corpuscles.  If  this  occurred  with  sufficient 
vigor  all  the  spores  were  disposed  of  and  the  ani- 
mal recovered.  Sometimes,  however,  the  spores 
germinated  even  after  they  had  become  intracellu- 
lar, and  when  the  parasitic  cells  reached  maturity 
they  appareiitly  had  the  power  of  killing  the  leu- 
coc\i;es  through  the  agency  of  a  secretion  peculiar 
to  themselves.  In  the  event  that  the  latter  proc- 
ess was  sufficiently  extensive  the  tissues  were  soon 
overrun  with  parasites  and  death  resulted  from  a 
septicemic  condition.  The  observations  were  made 
in.  the  living  transparent  animal. 

Although  the  example  cited  seemed  convincing, 
Natural  it  Avas,  of  coursc,  neccssary  that  observations 
should  extend  over  many  infectious  processes  be- 
fore phagocytosis  as  the  cause  of  natural  immunity 
could  be  accepted  as  a  general  fact.  This  has  been 
done  on  rather  broad  lines  by  Metchnikoff  and  his 
pupils,  and  the  results  have  served  to  convince 
them  that  the  phagocytes  are  responsible  for  nat- 
ural immunity  in  all  instances,  and  that  the  de- 
gree of  natural  immunity  in  a  given  case  depends 
on  the  degree  of  phagocytosis  which  is  manifested 
against  the  organism.  x\s  stated  previously,  the 
microphage,  with  its  microcytase,  is  held  responsi- 
ble for  antibacterial  immunity  in  most  instances, 
although  the  macrophage  is  concerned  in  certain 
chronic  infections. 

If  an  animal  is  susceptible  to  a  virulent  culture 
of  anthrax,  but  resistant  to  a  weak  culture,  the 


TOXINS    AND    CHEM0TAXI8. 


185 


phagocytic  power  is  found  to  be  greater  for  the 
weaker  organism.  The  highly  virulent  culture 
creates  a  condition  of  negative  chemotaxis,  with 
the  consequence  that  leucocytes  are  not  attracted 
and  microbic  proliferation  proceeds  rapidly. 
Without  going  into  details,  studies  of  the  follow- 
ing and  perhaps  other  micro-organisms  have 
strengthened  Metchnikoff  in  his  views:  staphylo- 
cocci, streptococcus,  pneumococcus,  gonococcus, 
vibrio  of  cholera  in  infections  of  the  guinea-pig, 
the  vibrio  of  goose  septicemia  in  relation  to  the 
guinea-pig,  which  is  naturally  immune,  the  spi- 
rillum of  relapsing  fever,  tubercle  bacillus,  yeast 
cells  and  other  fungi,  and  certain  animal  para- 
sites (Trypanosoma  lewisii). 

Most  important  are  certain  conditions  which 
create  a  condition  of  negative  chemotaxis,  or  other- 
wise engage  the  phagoc3^es  so  that  they  refuse  to 
take  up  the  essential  organistm.  Vaillard  says 
that  all  animals  are  immune  to  pure  cultures  of 
the  tetanus  bacillus  or  its  spores,  provided  the  lat- 
ter have  been  washed  entirely  free  of  toxin.  The 
absence  of  toxin  permits  of  positive  chemotaxis 
and  phagocytosis,  whereas  toxin  when  present 
causes  negative  chemotaxis,  and  the  bacilli  pro- 
ceed to  further  toxin  formation.  The  same  is  held 
to  be  true  in  infections  by  some  other  organisms. 

It  seems  definitely  established  that  contaminat- 
ing organisms  (pyogenic  cocci.  Bacillus  prodigio- 
sus)  may  greatty  increase  the  virulence  of  the  ba- 
cillus of  symptomatic  anthrax,  Bacillus  aerogenes 
capsulatus  and  the  tetanus  bacillus — anaerobic  or- 
ganisms. On  the  one  hand,  the  secondary  bac- 
teria ma}^  produce  more  favorable  conditions  for 


Relation  of 
Phaciocytosis 
to  Virulence 
of  Bacteria. 


Toxins  as  Cause 
of   Negative 
Chemotaxis. 


Accidental 
Engagement 
of  Phagocytes. 


18G 


INFECTION  AND  IMMUNITY. 


Acquired 

Immunity 

to  Bacteria. 


Anthrax. 


the  growth  of  the  anaerobes  by  consuming  local 
oxygen,  or,  as  Metclmikoff  believes,  they  may  so 
engage  the  phagocytes  that  the  latter  have  no  dis- 
position to  take  up  the  essential  organism.  Tliis 
condition  may  be  an  important  one  in  other  mixed 
infections,  as  when  the  streptococcus  complicates 
diphtheria  and  scarlet  fever. 

If  the  phagocytic  poAver  is  an  index  of  the  de- 
gree of  natural  antibacterial  immunity,  is  the  same 
correspondence  to  be  recognized  when  the  immun- 
ity is  acquired?  To  answer  this  question  satisfac- 
torily it  is  necessary  to  bring  phagocytosis  in  rela- 
tion to  two  different  t5'pes  of  antibacterial  immun- 
ity which  it  is  possible  to  recognize.  Cholera  is  an 
example  of  that  type  of  antibacterial  immunity  in 
which  the  bactericidal  power  of  the  serum  under- 
goes a  great  increase.  It  is  stated  that  anthrax 
represents  another  type  in  which  the  immunity  is 
not  dependent  on  the  bactericidal  power  of  the 
seriim.  Probably  the  same  may  be  said  of  acquired 
immunity  to  the  streptococcus,  staphylococcus  and 
the  pneumococcus,  yet  it  is  perhaps  not  definitely 
established  that  the  immunity  in  these  instances 
is  antibacterial  rather  than  antitoxic.  For  the 
present  we  may,  however,  with  Metchnikoff,  con- 
sider that  the  immunity  is  antibacterial  and  that 
it  is  a  cellular  or  phagocytic  immunity. 

Eabbits  which  have  been  immunized  against 
anthrax  respond  to  subcutaneous  or  intraperitoneal 
injection  of  a  virulent  culture  by  concentrating  so 
vast  a  number  of  microphages  at  the  site  of  inocu- 
lation that  the  fluid  becomes  purulent  in  appear- 
ance. Examination  shows  an  enormous  degree  of 
phagocytosis.     When,  on  the  other  hand,  non-ira- 


INFLUENCE   OF  HE  RUM.  187 

mune  rabbits  are  submitted  to  similar  inocula- 
tions, the  fluid  which  accumulates  locally  is  of  a 
clear  serous  character,  contains  few  leucocytes,  and 
no  phagocytosis  is  observable ;  the  animals  die  of  a 
rapidly  developing  septicemia.  From  the  results 
one  may  well  suspect  that  the  immunity  is  related 
to  and  perhaps  coextensive  with  the  acquired  pha- 
gocytic power. 

But  is  the  serum  of  no  influence  ?  It  has  often  Phagocytes 
been  held  that  phagocytes  take  up  bacteria  only  yfr'^u^elTt 
after  the  latter  have  been  injured  or  killed  by  the  Bacteria. 
serum  or  plasma.  Metchnikofi:  answers  this  objec- 
tion experimentally  by  inoculating  an  immune  rab- 
bit with  anthrax,  withdrawing  some  of  the  exu- 
date at  a  time  when  phagocytosis  is  complete,  and 
injecting  it  into  a  non-immune  rabbit.  The  sec- 
ond animal  dies.  Since  none  but  phagocytized 
bacilli  were  injected  into  the  non-immune  rabbit 
( !),  and  since  the  latter  succumbs  to  anthrax,  it 
seems  not  only  unnecessary,  but  unjustiflable,  to 
assume  that  the  bacteria  must  be  attenuated  by 
the  serum  before  they  can  be  taken  up  by  the  leu-  -^^^  infruence 
oocytes.  May  the  serum,  nevertheless,  have  some  ofserum. 
obscure  action  which  may  not  be  included  under 
such  terms  as  bactericidal  and  attenuating?  It 
seems  fairly  well  established  that  anti-anthrax 
serum,  at  least  from  certain  animals,  may  exert  a 
protective  influence  when  injected  into  other  ani- 
mals in  conjunction  with  or  in  advance  of  the  cul- 
ture; 3'^et  Metchnikoff  discredits  the  importance  of 
such  protection  and  says  that  "those  properties  of 
the  body  fluids,  as  the  bactericidal,  preventive  and 
agglutinating,  fall  away  into  the  background  in 
such  examples  of  immunitj^"     It  is  the  tendency 


188  INFECTION  AND  IMMUNITY. 

'  of  the  school  of  Metchnikoff  to  refer  the  protective 
power  of  a  serum  to  its  faciilt}''  of  stimulating  the 
phagoc^-tes  rather  than  to  its  effect  on  the  micro- 
organisms. "We  shall  see,  however,  in  speaking  of 
opsonins  (p.  193)  that  even  in  relation  to  anthrax 
the  serum  may  possess  a  distinct  property  which 
facilitates  phagoc}i;osis,  not  by  stimulating  the 
phagoc}i;es  but  by  some  action  on  the  bacteria. 
Cholera  and  Concerning  those  diseases  in  which  immunity 
fections!  is  characterized  by  a  great  increase  of  the  bac- 
tericidal amboceptors  or  fixators,  Metchnikoff  does 
not  disregard  the  existence  or  importance  of  the 
immune  bodies,  but  rather  seeks  to  show  that  they 
are  a  product  of  phagocytic  activity.  The  con- 
ditions are  held  to  be  similar  to  those  already 
mentioned  in  connection  with  intra  vitam,  hemoly- 
sis. That  is  to  say,  microcytase  exists  only  in  the 
leucoc}i;es  of  the  immune  animal  under  normal 
conditions;  it  escapes  into  the  plasma,  or  into  the 
serum  during  coagulation,  only  as  a  consequence 
of  the  phagolysis  already  mentioned.  The  phe- 
nomenon of  Pfeiffer  occurs  only  because  the  in- 
jected culture  injures  the  leucocytes,  resulting  in 
the  liberation  of  microcytase,  which  in  conjunction 
with  the  fixators  causes  the  solution  of  the  vibrio. 
When  phagolysis  is  prevented  by  a  preceding  in- 
jection of  bouillon,  phagocvtosis  and  intracellular 
solution  of  the  organisms  entirely  supplant  extra- 
cellular solution. 
Intravascular  If  an  immune  animal  receives  an  intravascular 
and  Phagolysis.  injection  of  the  vibrio  of  cholera  and  is  sacrificed 
shortly,  the  relation  of  the  organisms  to  the  leu- 
coc)i;es  may  be  studied  in  stained  microscopic  sec- 
tions of  the  organs    (lungs).     Leucocytes  which 


FORMATION  OF  GYTA8E.  189 

have  undergone  phagolysis  are  seen  to  be  clumped 
in  the  pulmonary  vessels  and  in  their  immediate 
vicinity  one  finds  many  micro-organisms  which 
have  been  changed  into  the  characteristic  granules 
by  the  action  of  the  cytase  which  has  escaped  from 
adjacent  leucocytes.  Coincident  with  the  phe- 
nomenon of  phagolysis,  the  leucocytes  lose  their 
phagocytic  power;  hence,  no  bacteria  are  found 
within  the  leucocytes.  On  the  other  hand,  all 
those  vibrios  which  are  remote  from  the  leuco- 
cytes have  a  perfectly  normal  appearance.  Phago- 
lysis in  the  blood  stream  may  be  prevented.  Just  as 
in  the  peritoneal  cavity,  by  a  preceding  injection 
of  bouillon  into  the  vessels.  In  this  instance  when 
the  culture  is  injected  no  extracellular  solution  or 
transformation  of  the  organisms  into  granules 
takes  place,  but  as  in  the  peritoneal  cavity,  their 
destruction  is  accomplished  entirely  within  the 
microphages.  Metchnikoff  holds  to  the  correct- 
ness of  these  observations  and  interpretations,  al- 
though contradictory  results  were  obtained  by 
Pfeiffer  and  his  pupils.  As  further  evidence  that  wicrocytase  is 
cytase  does  not  exist  normally  in  the  plasma  Metch-  '"traceiiuiar. 
nikoff  cites  the  condition  which  is  found  in  the 
anterior  chamber  of  the  eye  in  immune  animals. 
The  vibrios  continue  unaffected  in  the  aqueous 
humor  until  such  a  time  as  leucocytes  wander  in, 
when  they  are  destroyed  by  phagocytosis.  Hence, 
cytase  does  not  exist  in  the  aqueous  humor,  and 
if  not  in  the  aqueous  humor  it  is  surely  absent 
from  the  plasma;  for  if  present  in  the  plasma  it 
would  reach  the  anterior  chamber  by  a  process  of 
diffusion.  Similar  conditions  prevail  in  edematous 
fluids.     In  another  instance  a  portion  of  a  vein. 


190  INFECTION  AND  IMMUNITY. 

filled  -with  blood,  was  resected  and  centrifugated 
without  the  formation  of  a  clot  (absence  of  pha- 
golysis)  ;  the  plasma  contained  no  cytase.  Also 
Gengou  collected  and  centrifugated  blood  in  tubes 
which  were  coated  with  paraffin,  and  thus  avoided 
clotting;  here  also  cytase  was  absent  from  the 
plasma. 
Increase  of  It  would  sccm,  then,  that  two  important  anti- 
of*Phaqocy"ic  bacterial  factors  characterize  immunity  to  cholera 
and  similar  infections :  the  development  of  specific 
fixators,  and  a  greatly  increased  phagocytic  power 
on  the  part  of  the  leucocytes.  Metchnikoff  leans 
to  the  view  that  bacteria,  having  absorbed  fixators, 
are  more  readiW  phagocytized,  but  no  clear  idea  is 
given  as  to  the  change  which  the  fixators  produce. 
However,  he  would  not  refer  the  increased  phago- 
ejtie  power  entirely  to  the  influence  of  the  fixa- 
tors. He  believes  that  the  leucoc}i;es  of  the  im- 
mune animal  have  per  se  a  higher  phagocHic 
power  than  that  of  the  normal  animal.  In  anthrax, 
for  example,  the  phagocytic  power  is  height- 
ened in  spite  of  the  fact  that  there  is  no  increase 
in  specific  fixators.  This  view,  however,  is  op- 
posed by  Denys  and  Leclef,  who  found  that  the 
leucocytes  of  the  immune  animal,  when  trans- 
ferred to  normal  serum,  had  no  greater  phago- 
cytic power  than  normal  leucocytes. 
Fixators  ]\Ietchnikoff  believes  that  fixators,  like  cytase, 
Microph^ge!  ^^*^  produced  by  the  microphage.  That  the  lymph- 
oid organs  may  form  certain  fixators  seems  prob- 
able from  the  observations  of  Pfeiffer  and  Marx 
in  regard  to  cholera  and  Wassermann  and  Takaki 
in  typhoid.  During  the  process  of  immunization 
and  at  a  time  when  amboceptors  were  absent  from 


ANTITOXIC   IMMUNITY.  191 

the  serum  they  could  be  demonstrated  in  tlie  blood- 
forming  organs  (spleen,  lymph  glands,  bone-mar- 
row) .  MetchnikofE  suggests  that  they  may  be  pro- 
duced in  these  organs  by  the  microphages  which 
have  wandered  in  after  having  englobed  the  micro- 
organisms. In  contrast  to  cytase  the  fixators  read- 
ily abandon  the  leucocytes  which  produced  ihera 
and  become  a  constituent  of  the  plasma. 

The  leucocytes  have  also  been  brought  in  rela-  Natural 
tionship  to  antitoxic  immunity  and  the  formation  [o  ToxTns. 
of  antitoxins.  In  experimental  tetanus  exudates 
which  are  rich  in  leucoc3^tes  contain  more  toxin 
than  does  a  similar  quantity  of  blood.  That  is  to 
say,  the  leucocytes  have  the  power  of  absorbing 
toxins,  and  it  is  held  that  the  natural  immunity 
of  the  animal  depends  on  the  degree  to  which  this 
power  is  present.  The  immunity  of  the  chicken 
to  tetanus  depends  not  on  non-susceptible  nerve 
cells  nor  on  the  presence  of  natural  antitoxin,  but 
on  the ' absorbing  power  of  the  leucocytes  for  the 
toxin.  'Not  only  do  leucocytes  absorb  toxins,  but 
it  is  held  that  they  also  are  the  producers  of  anti- 
toxins. As  compared  with  the  side-chain  theory, 
it  is  a  peculiarity  of  the  view  of  Metchnikoff  that 
antitoxin  does  not  represent  a  constituent  of  the 
tissue  cells,  but  rather  the  toxin  itself,  which  has 
been  altered  by  leucocytic  activity  in  a  manner  as 
yet  obscure. 

In   passive   antitoxic   immunity  the  idea   of   a  Passive 
chemical  union  between  toxin  and  antitoxin  does   J'Jilmu'nity. 
not  meet  with  general  acceptance  among  the  up- 
holders of  the  phagocytic  theory.     It  is  sometimes 
said  that  antitoxins  are  efficacious  from  the  fact 
that  they  stimulate  phagocytosis   (absorption)   of 


192  INFECTION  AND  IMMUNITY. 

the  toxin,  the  hitter  then  suffering  disintegration 
in  the  leucoc3^tes. 
Sumniary.       The  following  statements  summarize  the  pliago- 
cytic  theory  of  immunity  as  conceived  by  ]\Ietcli- 
nikoff : 

1.  Natural  immuiiity  to  bacteria  depends  on 
and  is  coextensive  with  phagocytosis  and  subse- 
quent digestion  of  the  microbes.  Intraleucocytic 
destruction  of  the  micro-organisms  is  accomplished 
by  tlie  C}i;ase,  possibly  aided  by  intraleucocytic  fix- 
ators. jSTormal  serum  is  devoid  of  both  fixators 
and  cytase. 

2.  Acquired  immunity  to  bacteria  depends  on 
the  establishment  of  a  heightened  phagocytic  power 
as  the  result  of  immunization  or  infection.  In 
disea=>es  like  anthrax,  in  which  fixators  are  not  in- 
creased, this  new  power  is  an.  acquired  property 
of  the  leucocjrtes  and  is  independent  of  any  in- 
fluence on  the  part  of  the  serum.  In  diseases  like 
cholera,  the  new  fixators  which  are  formed  may 
render  the  micro-organisms  more  susceptible  to 
phagocytosis,  but  this  is  probably  secondary  to 
increased  function  on  the  part  of  the  phagocytes. 
Both  cytase  and  fixator  are  produced  by  the  pha- 
gocytic cells.  In  acquired  active  immunity  to 
bacteria  the  fixators  may  be  free  in  the  serum 
and  plasma,  but  the  cytase  is  intracellular.  In  all 
cases  cytase  becomes  extracellular  only  as  the  re- 
sult of  phagolysis. 

3.  In  passive  immunity  to  bacteria,  as  when  an 
antibacterial  serum  is  injected  for  the  sake  of 
prophylaxis  or  cure,  the  serum  is  efficacious  chiefly 
because  it  stimulates  the  leucocytes  to  increased 
phagocytosis. 


SUMMARY;    OPSONINH.  193 

4.  Natural  immunity  to  toxins  depends  on  the 
power  of  the  leucocytes,  and  perhaps  the  genera- 
tive organs,  to  absorb  the  toxin. 

5.  Active  immunity  to  toxins  is  estal)lished 
througli  the  activity  of  the  leucocytes,  by  which 
the  toxin  is  probably  so  changed  as  to  constitute 
antitoxin. 

6.  In  passive  antitoxic  immunity  the  antitoxin 
presumably  acts  by  stimulating  the  phagocytes  to 
an  increased  absorption  of  the  toxin. 

Many  investigators  are  carrying  on  work  in  re-  opsonins. 
gard  to  phagocytosis  and  the  properties  of  serums 
from  a  point  of  vieAv  wbich  is  entirely  imbiased. 
From  sources  of  this  nature  discoveries  of  recent 
date  indicate  that  phagocytosis  of  micro-organisms 
by  the  leucocytes  is  impossible  without  the  aid  of 
some  property  in  the  serum.  It  seems  that  these 
substances,  which  tbe  discoverers,  Wright  and 
Douglas,  call  opsonins,  act  directly  on  the  bacteria, 
and  that  there  is  no  reason  to  suppose  that  their 
virtue  lies  in  a  stimulation  of  the  phagocj^tes  them- 
selves. The  facts  which  permit  of  this  deduction 
are  the  following :  1.  Wlien  the  fresh  defibrinated 
blood  of  some  animal  is  mixed  with  the  culture  of 
a  suitable  micro-organism  (staphylococcus,  strep- 
tococcus, anthrax  bacillus,  etc.)  and  placed  in  the 
thermostat  for  20  or  30  minutes,  stained  prepara- 
tions of  the  mixture  show  that  the  polymorphonu- 
clear leucocytes  contain  a  large  number  of  the  mi- 
crobes. 2.  If,  however,  all  the  serum  is  washed 
from  the  blood  before  adding  the  micro-organisms, 
practically  no  bacteria  are  ingested.  This  shows 
the  importance  of  the  serum,  but  does  not  differ- 
entiate between  some  effect  on  the  leucoc}i:es,  on 


194  IXFECTIOX  AXD  IMMUNITY. 

the  one  liand.  or  tlie  bacteria,  on  the  otlier.  3. 
In  order  to  decide  this  point  one  may  subject  the 
suspension  of  bacteria  to  the  action  of  fresli  cell- 
free  sernm.  and  after  a  contact  of  about  30  min- 
utes remove  all  the  serum  by  centrifugation,  and 
mix  the  "^sensitized"  culture  with  serum-free 
blood;  phagocytosis  occurs  almost  to  the  same  de- 
gree as  when  the  fresh  defibrinated  blood,  contain- 
ing serum,  is  used.  These  results  seem  to  show 
definitely  that  phagocytosis  depends  on  the  power 
of  the  opsonins  to  affect  the  bacteria  in  some  pe- 
culiar manner.  Opsonins  are  very  susceptible  to 
heat,  and,  like  complement,  disappear  spontane- 
ously from  the  serum  in  a  short  time.  Hektoen 
and  Ruediger,  and  Bulloch  and  Atkin  have  con- 
fi.rmed  the  observations  of  Wright  and  Douglas 
and  the  former  have  added  facts  of  importance. 
It  seems  that  opsonin  has  a  structure  like  that  of 
toxin,  i.  e.,  a  haptophorous  and  an  opsoniferous 
group ;  -"hj  heating  sensitized  bacteria  the  opson- 
iferous group  appears  tO'  be  destroyed,  but  the  in- 
active opsonin  (opsonoid)  by  saturating  the  re- 
ceptors of  the  bacteria  prevents  further  sensitiza- 
tion by  fresh  serum"  (Hektoen  and  Euediger). 
Various  salt  solutions  neutralize  the  opsonins. 
Opsonins  will  be  brought  into  still  more  important 
relationship  to  phagocytosis  if  it  can  be  shown 
detinitely  that  they  are  increased  as  the  result  of 
immunization  or  infection. 


CHAPTER  XV. 


THE  SIDE-CHAIN  THEORY  OF  EHRLICH  AND  ITS 

RELATION  TO  THE  THEORY  OF 

PHAGOCYTOSIS. 

In  1885,  before  the  discovery  of  toxins  and  anti-  side-thain 
toxins  and  before  there  was  any  knowledge  as  to  piied  to 
the  real  nature  of  immunity,  Ehrlich^  published  a 
small  volume  on  the  "Oxygen  Requirements  of  the 
Body.^'  Herein  the  belief  was  expressed  that  the 
assimilation  of  foods  by  cells  is  accomplished  only 
after  chemical  union  has  taken  place  between  the 
food  substance  and  some  constituent  of  cellular 
protoplasm.  It  is  not  the  understanding  that  as- 
similation is  at  an  end,  however,  when  this  union 
has  occurred,  for  certain  molecules  of  complex 
chemical  nature  and  of  great  size  must  be  split  up 
into  simpler  substances  before  they  can  enter  into 
the  composition  of  protoplasm.  Therefore,  the  cell 
constituent  which  combines  with  the  nutritious 
molecule  serves  only  as  a  link  to  bring  the  food- 
stuff into  relation  with  the  digestive,  oxidizing  or 
fermentative  activities  of  the  cell, 

Ehrlich  speais  of  that  portion  of  living  proto-  "Leistungs- 
plasm  which  represents  the  cellular  activities  as 
the  "Leistungshern"  of  the  cell,  the  center  of  cel- 
lular activity,  or  the  central  group  of  the  proto- 
plasm, whereas  those  chemical  groups  which  bind 
the  food  substances  are  called  the  side-chains  of  the 
"  Leistungskern." 

The  author  of  .the  theory  has  made  his  concep- 

1.  Ueber  das  SauerstofiEbedurfnis  des  Organismus. 


kern"  and 
Side-Chains. 


190  IXFECTIOy  AND  IMMUNfTY. 

tioii  more  tangible  through  an  analogy  whirli  was 
drawn  with  the  so-called  ring  or  nnoknis  of  benzol 
and  its  side-chains.  The  molecule  of  benzol,  CgHg, 
has  a  definite  formation  in  which  each  carbon 
atom  is  linked  to  two  others  in  such  a  manner  as 
to  form  a  ring;  three  valences  of  each  carbon 
atom  are  satisfied  in  this  way,  and  the  fourth  is 
satisfied  by  atoms  of  hydrogen,  one  of  which  is  at- 
tached to  each  carbon  atom,  thus : 

H 

I 

C 

/  -^ 
H-C       C-H 

II  i 

H-C  C-H 

\  II 

C 

i 

This  ring  is  analogous  to  the  "LeistuDgsl-cni"  of 
the  cell.  A  great  variety  of  chemical  compounds 
exists  and  very  many  may  be  produced  syntheti- 
cally by  substituting  for  one  or  more  atoms  of 
hydrogen,  one  or  more  other  groups  of  atoms  which 
may  be  ver}-  simple  or  very  complex.  Tlie  groups 
which  have  been  substituted  are  called  side-chains. 
Thus  benzoic  acid  is  formed  from  benzol  by  sub- 
stituting the  acid  radical  COOH  for  a  particular 
H,  and  the  COOH  in  this  instance  is  a  side-chain 
of  the  ring : 

o 

c 

I^OH 
C 
/    ^ 
H-C        C-H 

II         J 
H-C        C-H 

C 


SIDE-CHAfNl^.  197 

Just  as  the  side-chains  of  the  "Leistungslcern" 
may  combine  with  food  particles,  so  may  the  side- 
chains  of  the  benzol  ring  combine  with  other 
groups  of  atoms  and  thereby  assimilate  the  latter, 
so  to  SEiy,  into  the  ring.  To  choose  a  simple  exam- 
ple, the  sodium  of  sodium  hydroxid  may  unite  with 
the  side-chain  COOH  to  form  sodium  benzoate, 
the  hydrogen  of  the  acid  radical  being  replaced  by 
the  sodium,  thus : 

o 

c 

C 

/  -^ 
H-C       C-H 

II         1 

H— C       C-H 

\  ^. 

C 

I 

H 

Presumabl}^  it  is  in  some  such  manner  as  sodium 
is  brought  into  relationship  with  the  benzol  nu- 
cleus, in  the  example  cited,  that  the  food  sub- 
stances are  brought  into  relationship  with  the 
''Leistungskern"  of  the  cell. 

The  hypothesis  of  Ehrlich  carries  with  it  the  Haptophores. 
assumption  that  the  side-chains  of  a  cell  possess  or 
consist  of  definite  groups  of  atoms  capable  of  unit- 
ing chemically  with  certain  other  definite  groups 
of  atoms  in  the  food  particles ;  hence  both  the  side- 
chain  and  the  food  substance  have  combining 
groups — haptophores.  The  side-chains  of  the  cells 
Ehrlich  now  calls  receptors,  elements  which  we 
have  already  recognized  in  connection  with  im- 
munity. Inasmuch  as  different  foods  have  differ- 
ent chemical  compositions,  it  is  likely  that  their 
binding  groups  are  not  identical;  and  if  this  be 


198  lyFECTIOy  AXD  IMMUyiTY. 

true  there  must  exist  luany  kinds  of  receptors, each 
of  which  is  able  to  unite  only  with  that  food  sub- 
stance Mhich  has  a  corresponding  binding  group  of 
atoms. 

In  contrast  to  the  condition  with  respect  to 
foods,  it  is  held  that  chemical  substances  of  Imown 
composition,  drugs  and  alkaloids  never  become  in- 
corporated as  a  part  of  the  protoplasm,  that  is, 
they  do  not  unite  with  cell  receptors,  although 
the}'  may  affect  the  vitality  and  function  of  proto- 
plasm profoundly.  Their  inability  to  yield  anti- 
bodies as  a  result  of  immunization  is  supposed  to 
depend  on  this  condition.  Such  substances,  ac- 
cording to  Ehrlich,  exist  in  the  cell  in  a  condition 
of  unstable  salt  formation  with  some  constituent 
of  the  protoplasm,  or  in  a  state  of  solid  solution. 

The  following  statement  from  a  recent  publica- 
tion by  Ehrlich  summarizes  the  nutritional  aspect 
of  the  theory:  "We  must  assume  that  all  sub- 
stances which  enter  into  the  structure  of  proto- 
plasm are  fixed  chemically  by  the  protoplasm.  We 
have  always  distinguished  between  assimilable  sub- 
stances which  serve  for  nutrition  and  which  enter 
into  permanent  union  with  the  protoplasm,  and 
those  which  are  foreign  to  the  body.  No  one  be- 
lieves that  quinin  and  similar  substances  are  as- 
similated, that  is,  enter  into  the  composition  of  the 
protoplasm.  On  the  other  hand,  the  food  sub- 
stances are  bound  in  the  cells,  and  this  union  must 
be  considered  as  chemical.  One  can  not  extract  a 
sugar  residuum  from  cells  with  water,  but  must 
first  split  it  off  with  acids  in  order  to  set  it  free. 
But  now  such  a  chemical  union,  like  every  syn- 
thesis,   demands    the    presence    of    two    binding 


APPLICATION   TO  IMMUNITY.  199 

groups  of  maximal  chemical  affinity,  which  are 
suited  one  to  the  other.  The  binding  groups  which 
reside  in  the  cells  and  which  bind  food  substances 
I  designate  as  side-chains  or  receptors,  while  I 
have  called  those  of  the  molecules  of  foodstuffs  the 
haptophorous  groups.  I  also  assume  that  proto- 
plasm is  endowed  with  a  large  series  of  such  side- 
chains,  which  through  their  chemical  constitution 
are  able  to  bind  the  difEerent  foodstiiffs  and  there- 
by provide  the  prerequisite  for  cellular  metabol- 
ism." 

If  the  side-chain'  theorv  of  nutrition  is  to  be-  sjde-chain 

"  ...  Theory  Ap- 

come  the  side-cham  theory  of  immunity  it  is  nee-  plied  to 
essary  that  it  undergo  elaboration  in  order  that  the 
formation  of  antibodies  may  be  adequately  ex- 
plained. If,  as  Ehrlich  assumes,  the  union  of 
toxin  with  cell  receptors, causes  the  overproduction 
of  the  latter  as  antitoxin,  and  if  this  union  is  an- 
alagous  to  that  of  food  substances  with  similar  re- 
ceptors, one  may  wonder  that  antibodies  are  not 
formed  for  our  ordinary  foods,  antibodies  which 
would  be  discharged  from  the  cells  and  which 
would  unite  with  circulating  nutritious  particles 
and  thereby  bring  about  a  condition  of  starvation. 
Without  entering  into  the  intricacies  of  this  ques- 
tion, it  seems  probable  that  normally  a  condition 
of  ph5^siologic  equilibrium  exists  between  the  food 
substances  on  the  one  hand  and  the  cellular  activi- 
ties on  the  other,  so  that  the  union  of  food  with 
protoplasm  constitutes  no  abnormal  stimulus  to 
the  " Leistungskern"  of  the  cell.  When,  however, 
cells  are  diverted  from  their  normal  metabolic 
function  by  union  with  toxins  and  other  "abnormal 
food   substances,"   the   effect   on   the   cell   is    de- 


200 


IXFECT/i)\    W  I)  I  \l  \IIMTY. 


scri])od  as  a  coll  doroet,  the  dofoct  consisting-  of  tlie 
functional  elimination  of  the  receptor.  The  "Leis- 
tungskcrn'  as  the  vital  or  regulating  center  of  the 
cell  repairs  the  defect  by  the  formation  of  new  re- 
ceptors, and  in  harmony  with  the  hypothesis  of 
Weigert  produces  not  only  enough  to  repair  the 
defect,  but  a  great  excess,  with  the  result  that 
many  are  tliroAvn  into  the  circulation.     The  anal- 
ogy of  the  "Leistungsl-crn"  with  the  benzol  ring 
can  not  be  carried  to  this  extent,  for  the  latter  has 
no  power  of  reproducing  side-chains  to  take  the 
place  of  one  which  has  been  bound  by  some  new 
group  of  atoms. 
Essential       It  will  bc  appropriate  in  this  place  to  consider 
Ehriich's  the  character  of  the  proof  wliich  has  hoen  offered 
**"^^"  in  support  of  the  three  tenets  which  constitute  the 
framework  of  the  theory  of  Ehrlich.     Tlicse  three 
tenets  may  be  expressed  as  follows :     1.  Antitox- 
ins counteract  toxins  by  entering  into  chemical 
union  with  them ;  a  similar  imion  takes  place  be- 
tween other  antibodies  and  their  homologous  sub- 
stances.     2.  Toxins    in    injuring    cells    combine 
chemically  with  a  definite  constitiient  of  the  proto- 
plasm, the  cell  receptor;   other   antigenous   sub- 
stances- enter  into  similar  union  with  the  appro- 
priate receptors  of  cells.   3.  Tlie  specific  antibodies 
of  the  serum  are  new-formed  receptors  identical  in 
structure  with  those  which,   as  cell  constituents, 
had  combined  with  the  homologous  antigens. 

First  tenet :  In  the  early  days  of  studies  on  im- 
munity (1890-1897),  the  action  of  a  toxin  and  the 
efficacy  of  an  antitoxin  could  be  determined  only 


Chemical  Union 

of  Antibodies 

with  Antigens. 


2.  An  antigen   or  an   antisenous   siil)stanoe   is  one  Avliich 
is  able  to  cause  the  formation  of  an  antibody. 


TOXm  AND  ANTITOXIN.  201 

by  injecting  these  substances  into  living  animals, 
and  the  animal  experiment  naturally  continues  to 
be  the  means  of  testing  the  curative  and  prophy- 
lactic values  of  serums.  So  long,  however,  as  such 
experiments  were  performed  exclusively  in  the  liv- 
ing animal  the  nature  of  the  action  of  antitoxin 
remained  to  a  certain  extent  in  doubt.  It  re- 
mained uncertain  wdiether  antitoxin  is  protective 
because  it  actually  destroys  the  toxin,  because  neu- 
tralization of  a  chemical  nature  occurs,  or  because 
in  some  manner  it  increases  the  resistance  of  the 
inoculated  animal.-  In  Chapter  viii,  p.  78,  experi- 
ments were  cited  to  show  that  antitoxin  does  not 
destroy  the  toxin,  and  this  is  generally  admitted  to- 
day. There  continues  to  be  some  difference  of  opin- 
ion, however,  in  relation  to  the  two  other  possibili- 
ties, i.  e.,  as  to  wdiether  antitoxin  combines  chemi- 
cally with  toxin,  or  is  efficacious  because  of  its 
stimulating  power  on  the  tissues  of  the  animal. 
Behring,  the  discoverer  of  antitoxin,  was  from  the 
beginning  an  exponent  of  the  chemical  theory,  even 
at  a  time  when  the  conceptions  of  Ehrlich  had  not 
been  fully  developed.  On  the  other  hand,  certain 
noted  investigators,  especially  Eoux  and  Buchner, 
and  later  Metchnikoff,  stood  for  the  alternative 
view. 

Following  closely  on  Behring's  great  discovery,  Ricmand 
Ehrlich  studied  the  hemagglutinating  toxin  ricin, 
from  the  castor-oil  bean,  and  by  immunization 
with  it  produced  a  specific  antitoxin,  i.  e.,  anti- 
ricin.  Eicin  is  toxic  to  er}i:hrocytes  both  in  the 
animal  body  and  in  the  test-tube,  and  if  it  could 
be  shown  that  antiricin  protects  in  the  test-tube 
by  a  direct  effect  on  the  toxin,  it  was  highly  prob- 


Antiricin. 


202 


INFECTION  AND  IMMUNITY. 


ChemicalNature 
of  the  Neutrali- 
zation of  Toxins 
by  Antitoxins- 


able  tliat  its  action  in  the  animal  body  wonld  be  of 
a  similar  nature.  The  resnlts  left  no  donbt  in  the 
mind  of  Ehrlich  that  antiricin  unites  chemically 
with  ricin,  and  the  applicability  of  this  principle 
in  animal  experiments  became  all  the  more  ap- 
parent when  it  was  shoT\'n  that  the  proportion  of 
antiricin  which  protects  in  vitro  also  protects  in 
rivo.  It  is  held  that  similar  proof  of  chemical  union 
between  bacterial  hemolysins,  the  hemolysin  of 
venom  and  the  leucocidin  of  the  staphylococcus 
with  their  respective  antitoxins  is  equally  valid. 
Altliough  the  animal  body  can  not  be  dispensed 
with  in  testing  the  action  of  the  antitoxins  of 
diphtheria  and  tetanus,  certain  principles  of  chem- 
ical action  are  found  to  prevail  which  leave  no 
doubt  in  regard  to  the  chemical  neutralization  of 
the  toxins.  If  neutralizing  proportions  of  diph- 
theria toxin  and  antitoxin  be  mixed  in  a  test-tube 
and  injected  immediately,  the  serum  does  not  af- 
ford absolute  protection;  if,  however,  the  mixture 
is  allowed  to  stand  for  from  fifteen  to  twenty  min- 
utes before  injection,  the  protection  is  absolute. 
This  alone  would  point  to  an  action  of  the  anti- 
toxin on  the  toxin,  for  the  completion  of  which  a 
certain  amount  of  time  is  required.  For  the  com- 
plete neutralization  of  tetanus  toxin  by  its  anti- 
toxin about  forty  minutes  are  necessary  at  ordinary 
temperatures.  Then  certain  other  chemical  princi- 
ples described  in  Chapter  viii,  p.  79,  are  found  to 
hold  true:  That  neutralization  proceeds  more 
rapidly  at  higher  than  at  lower  temperatures,  more 
rapidly  in  concentrated  than  in  dilute  solutions, 
and  that  it  takes  place  in  accordance  with  the  law 
of  multiple  proportions. 


AMBOCEPTORS,  ETC.  203 

Granting,  then,  that  neutralization  of  toxin  by 
antitoxin  is  of  a  chemical  nature,  the  first  essential 
step  in  the  chemical  or  side-chain  theory  is  estab- 
lished. If  antitoxin  combines  chemically  with 
toxin,  union  must  occur  through  combining  groups 
which  each  molecale  possesses.  Herein  lies  the  ex- 
perimental justification  for  assuming  the  existence 
of  haptophorous  groups. 

The  situation  is  more  difficult  in  regard  to  the   Union  of  Aggiu- 

n  •     T  -I  tinin  and  Ambo- 

union  of  receptors  of  the  second  and  third  orders,  ceptors  with 
i.  e.,  agglutinins  and  amboceptors  with  the  ho- 
mologous receptors  of  bacteria  and  other  cells. 
One  can  not  titrate  bacteria  against  agglutinin  or 
bactericidal  amboceptors  so  exactly  as  toxin  can  be 
titrated  against  antitoxin,  for,  in  the  first  place, 
it  is  difficult  to  obtain  at  will  a  desired  concentra- 
tion of  bacteria  and  to  keep  it  without  alteration, 
and,  in  the  second  place,  bacterial  cells  contain 
many  more  receptors  than  are  necessary  for  their 
agglutination  and  solution.  A  given  mass  of  bac- 
teria will  take  up  varying  quantities  of  agglutinin, 
depending  on  the  concentration  of  the  latter,  and 
the  same  principle  applies  to  the  absorption  of 
bactericidal  and  hemolytic  amboceptors.  As  more 
and  more  agglutinin  is  added,  the  total  amount 
absorbed  increases  with  each  addition,  although 
the  ratio  of  absorbed  to  unabsorbed  agglutinin 
grows  less  continuously.  The  conditions  which 
govern  this  phenomenon  are  not  understood. 
Perhaps  no  condition  speaks  more  decisively  for 
chemical  union  of  these  bodies  with  cell  receptors 
than  immunization  experiments  which  were  car- 
ried on  with  cells  which  had  been  treated  with  a 
great  excess  of  the  specific  antiserum.     The  as- 


J04 


lyPECTIOX  AXD  IMMUMTY 


sumption  was  made  that  if  one  coukl  force  all  the 
recc})tors  of  orvthrocvte:?,  for  example,  to  take  \\]) 
the  specific  amboceptors,  such  corpuscles  should 
lose  their  power  to  cause  the  formation  of  a  hemo- 
l^-tic  serum  when  injected  into  a  suitable  animal. 
This  would  follow  logically,  for  the  receptors  of 
the  corpuscles,  being  already  bound,  would  not  be 
free  to  unite  with  receptors  of  the  immunized  ani- 
mal. Antibodies  were  not  formed  under  these  cir- 
cumstances, from  which  it  is  concluded  that  the 
receptors  of  the  er}i;hroc3'tes  had  united  chemi- 
cally with  the  antibodies  of  the  serum  (Sachs). 
In  order  to  completely  occupy  all  the  receptors  of 
the  vibrio  of  cholera  Pfeiffer  used  3,000,000  to 
4.000,000  times  the  dissolving  amount  of  the  anti- 
cholera  serum.  Although  the  mere  absorption  of 
agglutinins  and  amboceptors  by  the  homologous 
cells  is  cited  in  favor  of  the  chemical  hypothesis, 
we  may  bear  in  mind  the  contention  of  certain  in- 
vestigators that  this  absorption  is  physical  rather 
than  chemical. 

Second  tenet :  What  evidence  have  we  that  tox- 
ins  and   other  antigenous   substances  enter   into 
Antigens  with  chemical  union  with  receptors  in  the  cells  of  the 

Cell   Receptors.     .  .  .  ^ 

immunized  animal?  It  is  probable  that  no  ob- 
servation speaks  more  strongly  in  favor  of  such 
union  than  a  famous  experiment  of  "Wassermann's 
in  which  the  central  nervous  system  of  guinea- 
pigs  was  ground  up  with  tetanus  toxin,  the  mix- 
ture allowed  to  stand  for  a  short  time  and  then 
injected  into  mice.  The  mixture  was  found  to  be 
non-toxic,  and  further  experiments  showed  that 
the  neutralizing  power  resides  in  the  solid  tissue 
in  the  emulsion.     It  is  claimed  bv  Ehrlich  that 


ChemicalNature 
of  Union  of  Tox- 
ins   and    Other 


UNION  WITH  CELLS.  205 

this  experiment  demonstrates  positively  that 
chemical  union  of  tetanus  toxin  takes  place  with 
constituents  of  the  nervous  tissue.  The  toxin  hav- 
ing been  completely  neutralized  can  not  again  be 
extracted  from  the  tissue.  The  condition  is  the 
opposite  in  relation  to  some  poisonous  alkaloids, 
as  strychnin,  which  it  appears  does  not  combine 
Avith  the  protoplasm  firmly  and  may  again  be  ex- 
tracted by  simple  methods. 

Von  Dungern  conducted  very  important  work 
with  the  precipitins,  which  is  interpreted  as  show- 
ing that  albuminotis  substances  other  than  toxins 
are  taken  up  chemically  by  the  cells.  He  injected 
considerable  quantities  of  a  foreign  serum  into  the 
veins  of  rabbits  and  studied  its  disappearance  from 
the  blood  of  the  injected  animal.  Traces  of  the 
foreign  serum  could  be  recognized  by  treating  the 
rabbit  serum  with  a  specific  precipitin  for  the  for- 
mer, the  precipitin'  having  been  obtained  pre- 
viously by  the  immunization  of  other  animals. 
The  foreign  serum  disappeared  from  the  circula- 
tion of  the  rabbit  with  some  rapidity  and  since  it 
could  not  be  demonstrated  in  the  excretions,  it 
seemed  necessary  to  assume  that  it  had  been  bound 
by  the  cells,  that  is  to  say,  by  the  cell  receptors. 

Third  tenet:  Is  there  any  direct  experimental  Proliferation 
proof  that  those  constituents  of  cells  which  have 
been  designated  as  cell  receptors  actually  undergo 
multiplication  in  the  cell  itself  as  a  preliminary  to 
their  discharge  into  the  circulation  in  the  form  of 
antibodies?  If  this  condition  could  be  demon- 
strated in  one  instance,  one  might  reasonably  con- 
sider that  it  typifies  a  law  according  to  Avhich  all 
antibodies   are  formed.     Further  experiments  by 


of  Receptors. 


20ti  IXFECTIOX  AXD  IMMVSITY. 

von  Dungern  Avitli  the  precipitins  seem  to  show 
that  such  intracellular  overproduction  actually 
does  occur.  The  experiments  concern  the  fate  of 
";^[ajaphlslna"'  (plasma  of  the  crawfish)  wlien  in- 
jected into  the  circulation  of  tlio  ral)l)it  (see 
above).  If  a  single  injection  of  the  serum  is 
given,  a  specific  precipitin  for  the  latter  body  in 
due  time  may  be  demonstrated  in  the  serum  of  the 
rabbit.  Eventually  the  precipitin  disappears  from 
the  circulation  by  excretion  or  other  means.  At 
that  time,  when  all  the  precipitin  has  disappeared, 
one  may  assume  that  the  cells  of  the  animal  still 
contain  an  increased  number  of  precipitin  recep- 
tors, although  the  latter  are  no  longer  produced  to 
such  an  extent  that  they  are  thrown  into  the  cir- 
culation. If  this  condition  exists  the  tissues  of 
the  animal  at  this  time  should  be  able  to  absorb  a 
larger  amount  of  the  foreign  serum,  given  in  a  sec- 
ond injection,  and  perhaps  absorb  it  more  rapidly 
than  the  tissues  of  an  untreated  rabbit.  Using  a 
specific  precipitating  serum  in  order  to  detect 
traces  of  the  foreign  serum  which  still  remained  in 
the  blood  of  the  injected  animal,  von  Dungern  de- 
termined that  its  tissues  actually  do  absorb  the 
plasma  more  rapidly  than  do  the  tissues  of  the 
untreated  rabbit.  The  cells  of  the  former  have  a 
greater  absorbing  power,  i.  e.,  a  greater  binding 
power  for  the  plasma;  therefore,  an  increased 
number  of  receptors. 

These  examples  are,  perhaps,  sufficient  to  illus- 
trate the  principles  of  experimentation  which  have 
been  followed  in  the  attempt  to  obtain  definite 
proof  of  the  correctness  of  the  essential  points  of 
the  theory.    The  results  are  in  entire  accord  with 


OTHER   TENETS.  207 

,  the  primary  assumptions  and  show  that  the  tlioory 
continues  to  serve  as  an  explanatory  basis  for 
newly-discovered  facts,  and  as  a  foundation  on 
which  new  researches  may  be  instituted. 

In  addition  to  the  three  main  principles  treated   other  import- 
of  above,  the  following  points  are  necessarily  in-   of  EiTrVich.**'** 
eluded  in  a  summary  of  the  views  of  Bhrlich,  many 
facts  of  a  corroborative  nature  having  l^ecn  ascer- 
tained in  independent  laboratories. 

1.  The  recognition  of  different  types  of  tissue 
receptors  by  Mdiich  peculiarities  in  the  action  of  the 
different  antibodies  are  explained.  Eeceptors  of 
the  first  order,  as  antitoxins,  anticomplements  and 
antiamboceptors,  are  regarded  as  relatively  simple 
bodies  because  no  other  constituent  can  be  recog- 
nized than  the  haptophorous  group  by  which  they 
combine  with  their  homologous  substances.  Ee- 
ceptors of  the  second  order  are  more  complicated 
in  that  they  have  something  more  than  the  mere 
binding  power;  usually  they  are  able  to  produce 
some  observable  change  in  the  substance  with 
which  they  unite.  Hence,  each  has  a  toxophorous 
or'  a  zymotoxic  group  in  addition  to  the  hapto- 
phorous, and  the  two  groups  are  part  of  the  same 
molecule.  Toxins,  agglutinins,  precipitins  and 
complements  are  receptors  of  the  second  order. 
Receptors  of  the  third  order,  i.  e.,  the  bacterio- 
lytic, hemolytic  and  cytotoxic  amboceptors,  are 
still  more  complex  in  that  they  are,  so  to  say,  only 
partial  antibodies,  the  complete  body  consisting  of 
the  amboceptor-complement  complex.  The  ambo- 
ceptor is  not  an  active  body,  but  serves  as  an  in- 
termediary body  to  connect  the  active  substance, 
complement,  with  the  cell.    In  the  cytolytic  proc- 


20S  IXFECTIOX  A.\D  IMMUyiTY. 

ess  the  amboceptor  tliroiigh  its  cytophilous  hapto- 
pliore  first  unites  with  tlie  cell,  and  as  a  result 
acquires  an  increased  affinity  for  complement, 
with  AA'liich  it  unites  through  its  complcmcnto- 
pliilous  haptophore.  Only  after  this  double  union 
is  completed  may  complement  affect  the  cell. 
From  this  it  follows  that  complement  in  the  cyto- 
l3i;ic  process  does  not  combine  with  the  cell  di- 
rectly. As  previously  stated,  Bordet  and  others 
oppose  the  idea  that  the  absorption  of  tliese  bodies 
is  of  a  chemical  nature,  considovinu-  it  railicv  to  he 
a  physical  process. 

Ehrlich  has  intimated  liis  belief  tliat  tissue  am- 
boceptors play  the  chief  role  in  the  fixation  of 
foods  by  the  cells  of  the  body. 

2.  The  chemical  theory  explains  the  specificity 
which  characterizes  the  formation  and  action  of 
antibodies.  Every  antigen  has  a  haptophore  which 
is  different  from  those  of  other  antigens;  conse- 
quently, it  unites  only  with  the  corresponding  cell 
receptor,  and  the  latter  w^hen  overproduced  and 
cast  into  the  circulation  retains  its  specific  liinding 
power  for  the  corresponding  antigen. 

3.  The  multitude  of  antibodies  w'hic]i  liave  been 
obtained  indicate  that  the  cells  contain  a  vast 
number  of  different  receptors  which  correspond  to 
the  three  types  now  recognized ;  that  is.  there  is  a 
different  antitoxin  receptor  for  every  kind  of 
toxin,  etc. 

4.  Ehrlich  has  limited  the  application  of  tlie 
term  toxin  to  those  substances  of  animal  or  plant 
origin,  immunization  with  which  causes  tlie  forma- 
tion of  specific  antitoxins.  Other  characteristics 
have  been  given  in  Chapter  vii,  p.  G5, 


COMPLEXITY  OF  TOXINS.  209 

5.  Receptors  of  the  second  order,  toxins,  agglu- 
tinins, precipitins  and  complements,  undergo  a 
peculiar  degenerative  change,  spontaneously  or  as 
a  result  of  exposure  to  injurious  agents,  in  wliich 
the  toxophorous  or  zymotoxic  group  disappears  or 
is  rendered  inactive.  The  termination  -oid  is  af- 
fixed to  the  altered  bodies,  as  toxoid,  agglutinoid, 
precipitoid  and  complementoid,  Wechsberg  has 
described  a  similar  degeneration  of  one  of  the  hap- 
tophores  of  amboceptors,  calling  the  product  am- 
boceptoid.  Toxoids  and  complementoids  on  im- 
munization cause  the  formation  of  corresponding 
antitoxins  and  anticomplements,  by  virtue  of  re- 
tention of  their  haptophorous  groujDs. 

6.  By  means  of  a  special  technic  devised  for 
studying  the  neutralization  of  toxin  by  antitoxin, 
i.  e.,  the  partial  saturation  method,  Ehrlich  found 
diphtheria  toxin  to  be  a  very  complex  substance. 
Not  all  the  molecules  of  the  toxin  have  the  same 
affinity  for  antitoxin,  and  according  to  the  de- 
grees of  their  affinity  have  received  the  names  of 
prototoxin,  deuterotoxin  and  tritotoxin.  Simi- 
larly, protoxoids  and  syntoxoids  are  molecules  of 
toxoid  having  different  affinities  for  antitoxin. 
These  conditions  are  represented  graphically  by 
means  of  the  "toxin  spectrum"  described  pre- 
viously. 

7.  Ehrlich  claims  that  the  diphtheria  bacillus 
secretes  two  toxins,  one  of  which  causes  the  acute 
manifestations  of  diphtheritic  intoxication,  where- 
as the  second  toxin,  i.  e.,  toxon,  has  a  prolonged 
incubation  period  and  probably  causes  diphtheritic 
paralysis.  Toxon  has  a  lower  affinity  for  diph- 
theria antitoxin  than  the  other  constituents  of  the 


210  IXFECTIOX  AXD  IMMUXITY. 

toxin  solution,  but  is  neutralized  bv  tbe  same  anti- 
toxin. Tbis  view  is  strongl}^  opposed  by  Arrbe- 
nius  and  Madsen,  wbo,  working  on  tbe  basis  that 
the  neutralization  of  toxin  takes  place  according 
to  certain  laws  of  physical  chemistry,  claim  that 
toxon  is  nothing  more  than  toxin  which  has  disso- 
ciated from  the  toxin-antitoxin  molecule. 

8.  It  is  thought  that  the  incubation  period 
which  characterizes  the  action  of  toxins  represents 
to  a  large  degree  the  time  required  for  the  action 
of  the  toxophorous  group  after  the  toxin  has  been 
bound  by  the  cells. 

9.  Ehrlich  stands  for  the  multiplicity  of  com- 
plements in  opposition  to  Bordet  and  others  who 
claim  the  existence,  of  but  one  complement 
(alexin).  The  various  complements  differ  in  the 
nature  of  their  haptophores,  without  regard  to 
possible  dijfferences  in  their  zymotoxic  groups. 

10.  Only  those  organs  which  have  suitable  re- 
ceptors may  produce  an  antibody  for  a  given  anti- 
gen, i.  e.,  only  those  cells  which  may  enter  into 
chemical  combination  with  the  antigen.  It  does 
not  follow,  however,  that  only  those  organs  which 
show  clinical  or  anatomic  lesions  may  produce, 
say,  an  antitoxin;  for  other  organs  not  so  suscep- 
tible to  the  action  of  the  toxin  may  still  possess 
the  suitable  receptors  and  cast  them  out  as  anti- 
toxin. 

Causes  of  Dif-       The  various  types  of  immunity  are  explainable 
oMmimJnity!  On  the  basis  of  the  side-chain  theory  in  the  follow- 
ing terms: 

1.  Natural  immunity  to  toxins  may  depend  on 

(a)  a  lack  of  suitable  cell  receptors,  the  toxin  con- 

.  sequently  finding  no  point  of  attack;  (h)   a  very 


TYPES  OF  IMMUNITY.  211 

low  affinity  between  cell  receptors  and  toxin  so 
.that  the  latter  does  not  unite  with  the  cells  except 
•under  special  conditions  (e.  g.,  the  immunity  of 
chicken  to  tetanus)  ;  or  (c)  on  the  presence  of 
natural  antitoxins. 

2.  Acquired  active  antitoxic  immunity  depends 
on  the  multiplication  and  excretion  of  cell  recep- 
tors (antitoxin)  into  the  circulation,  the  new- 
formed  bodies  having  the  power  of  combining 
chemically  with  additional  toxin  which  may  be  in- 
troduced. 

3.  Passive  antitoxic  immunity,  as  established  by 
the  injection  of  an  antitoxin,  depends  on  the  abil- 
ity of  the  antitoxin,  to  combine  chemically  with  the 
toxin  and  thus  to  divert  the  latter  from  the  cells. 

4.  Natural  immunity  to  bacteria  depends  on  (a) 
a  lack  of  suitable  cell  receptors  with  which  the 
toxic  bacterial  constituents  might  combine;  (h)  a 
very  low  affinity  between  cell  receptors  and  the 
toxic  bacterial  constituents;  or  (c)  on  the  presence 
of  natural  bacteriolysins  (amboceptors  and  com- 
plements). 

5.  Acquired  active  antibacterial  immunity  de- 
pends on  the  multiplication  and  excretion  into  the 
circulation  of  specific  cell  receptors  (amboceptors) 
which  have  the  power  of  uniting  with  complement 
to  kill  the  micro-organisms  which  may  be  intro- 
duced. 

6.  Passive  antibacterial  immunity,  as  estab- 
lished by  the  injection  of  a  bacteriolytic  serum, 
depends  on  the  ability  of  the  amboceptors  con- 
tained in  the  serum  to  unite  chemically  with  the 
receptors  of  the  micro-organism,  as  a  result  of 
which  complement  is  absorbed  to  kill  and  perhaps 


212 


ixFEcriox  AXD  iMMixrry. 


Comparison  of 
Theories  of 
Fhrlich  and 
Metchnikoff. 


to  dissolve  the  Ijacteria.  The  (.'oniijlonient  may  be 
])rcsent  in  the  serum  ■which  is  injected,  or  the  nat- 
nriil  complement  of  the  individual  may  be  utilized 
by  the  amboceptors. 

When  one  seeks  to  compare  the  theory  of  Eln-lii'li 
witli  that  of  Metchnikoff,  one  finds  little  more  in 
common  than  the  general  purpose  of  explainino: 
the  ])henomena  of  immunity.  Yet  it  is  remark- 
able that  where  there  is  so  little  in  common  there 
are  so  few  contradictions  of  an  essential  nature. 

The  theory  of  Ehrlich  has  that  degree  of  defi- 
niteness  which  it  must  have  in  order  to  be  a  plausi- 
ble chemical  theory,  whereas  that  of  Metchnikoff 
seems  more  general  in  that  it  is  so  largely  biologic 
and  vitalistic. 

Each  has  a  certain  relation  to  nutrition.  Plia;i:o- 
cytosis  as  a  nutritional  measure  is  found  in  lower 
types  of  animals,  and  accomplishes  nothing  further 
than  to  bring  the  food  substance  in  contact  "\^'ith 
the  digestive  ferments  contained  in  the  cell.  Tu 
relation  to  nutrition  the  theory  of  Ehrlich  begins, 
so  to  sa}'',  where  the  phagoc}i;ic  theory  leaves  off, 
involving,  as  it  does,  the  method  by  which  food 
substances  become  a  part  of  the  protoplasm. 

Metchnikoff,  with  Ehrlich,  recognizes  the  vari- 
ous antiliodies  which  have  been  discovered.  The 
former  holds  that  all  are  produced  by  the  phago- 
cytes without  suggesting  clearly  a  method  Ijy 
which  they  may  be  formed.  Ehrlich  assumes  a 
very  precise  method  by  which  they  may  be  formed, 
but  designates  no  particular  cells  as  their  pro- 
ducers, stating  only  in  a  general  way  that  an  anti- 
body is  produced  only  by  those  cells  with  wliich  the 


FjHRLKJU    and    METCHNIKOFF.  213 

antigen  may  combine;  in  some  instances,  the  leu- 
cocytes may  be  snch  cells. 

The  theory  of  Metchnikoff  is  not  concerned  with 
the  structure  of  toxins  and  the  various  antibodies, 
nor  with  the  m.ethod  by  which  toxins  may  injure 
the  ceils,  whereas  Ehrlich  presents  delinite  concep- 
tions on  these  points. 

Both  recognize  that  there  is  more  than  one  com- 
plement (cytase).  Ehrlich  recognizes  no  limit  to 
the  varieties  which  may  exist,  whereas  Metehnikoff 
describes  but  two  cytases,  microcytase  and  macro- 
cytase. 

The  view  which  Metehnikoff  has  expressed,  tliat 
antitoxin  is  produced  by  some  action  of  the  phago- 
cytes on  the  toxin,  is  directly  opposed  to  that  of 
Ehrlich  which,  recognizes  antitoxin  as  a  product  of 
the  cell  itself, 

They  agree  that  amboceptors  (fixators)  become 
extracellular  in  the  blood. 

Metehnikoff  holds  that  complements  (cytases) 
are  produced  only  by  the  phagocytes  and  that 
these  substances  are  found  in  the  plasma  or  serum 
only  as  a  result  of  injury  to  the  phagocytes  (phago- 
lysis).  These  points  are  not  involved  essentially 
in  the  theory  of  Ehrlich.  Certain  investigators 
who  work  in  harmony  with  the  side-chain  theory, 
as  well  as  those  who  represent  the  views  of  Meteh- 
nikoff, have  extracted  complement  from  the  leuco- 
cytes. Some  of  Ehrlich's  supporters  believe  that 
complement  exists  normally  in  the  plasma. 

Metehnikoff  and  Ehrlich  hold  divergent  views 
concerning  the  action  of  antitoxins,  the  former  be- 
lieving that  antitoxins  stimulate  the  phagoc^iies  to 
an  increased  absorption  and  consequent  destruc- 


214  IXFECTIOy  AyO  IMMUNITY. 

tion  of  the  toxin,  Avhereas  Ehrlich  claims  that 
antitoxin  neutralizes  toxin  by  combining  chemi- 
cally with  it. 

According  to  Metchnikoff,  all  types  of  immunity 
depend,  directly  or  indirectl}',  on  phagocytic  activ- 
ity. Wliile  the  side-chain  theory  is  not  in  har- 
mony "with  such  a  broad  assumption,  it  carries 
with  it  no  denial  of  the  phenomenon  of  phagocyto- 
sis nor  of  its  importance  in  certain  infections. 

From  these  selected  considerations  it  is  seen 
Compatibility  ^^^^^  '*'''' ®  ^^™  theories  do  not  stand  to  each  other  in 
of  Theories.  j;]^q  relation  of  antitheses,  and  in  the  light  of  pres- 
ent laiowledge  it  would  seem  unwarranted  to  cling 
to  one  view  to  the  absolute  exclusion  of  the  other. 
It  does  not  follow  that  because  demonstrable 
serum  properties  explain  immunity  to  one  disease, 
or  to  a  certain  group  of  diseases,  that  recovery 
from  all  diseases  miist  depend  on  properties  of  the 
serum ;  nor  because  phagoc^^tic  activity  explains 
recovery  in  certain  instances  that  recovery  from 
all  diseases  must  depend  on  a  similar  activity.  The 
conditions  which  exist  in  each  disease,  of  course, 
must  be  recognized  independently.  It  so  happens 
that  recovery  from  a  certain  group  of  di'jeases, 
e.  g.,  staphylococcus,  streptococcus  and  pneumo- 
coccus  infections,  is  not  accompanied  by  the  de- 
velopment of  conspicuous  antitoxic  or  bactericidal 
properties  in  the  serum,  but  they  are  characterized 
by  a  great  increase  in  the  number  of  circulating 
leucoc3i:es  (microphages),  cells  of  lcno\\Ti  phago- 
c\i:ic  and  bactericidal  power,  whereas  the  opposite 
conditions  are  found  in  certain  other  diseases,  e. 
g.,  typhoid  and  diphtheria.  If  one  seeks  the  most 
apparent  explanation  in  each  case,  the  great  leuco- 


OPI^ONINS.  215 

cytosis  would  seem  to  be  of  prime  importance  in 
the  first  group,  and  the  antitoxic  and  bactericidal 
power  of  the  serum  in  the  second. 

Investigations  from  various  sources  render  un-  opsonins, 
questionable  the  value  of  phagocytosis  in  certain 
infections,  and  of  particular  significance  is  the 
work  concerning  opsonins  which  was  referred  to  in 
the  preceding  chapter.  From  this  work  it  follows 
that  even  for  the  phagocytic  destruction  of  bac- 
teria the  serum  contains  properties  which  are  of 
essential  importance.  This  appears  of  all  the  more 
importance  from  the  fact  that  immunization  with 
at  least  some  micro-organisms  (streptococcus, 
stajohylococcus)  causes  an  increase  in  opsonins  or 
bacteriotropic  substances. 

The  accompanying  illustration,  with  some  modi- 
fications, is  taken  from  "Ehrlich's  Seitenketten- 
theorie,''  by  Ludvig  Aschofl;.  The  cell  used  for 
immunization  is  assumed  to  be  a  cell  which  will 
cause  the  formation  of  antitoxin,  agglutinin  or 
precipitin,  and  bactericidal  amboceptors;  the 
diphtheria  bacillus  is  such  an  organism,  consider- 
ing toxin  as  one  of  the  receptors  of  the  bacillus. 
This  means  that  the  bacillus  is  able  to  cause  the 
overproduction  of  all  three  types  of  receptors.  The 
illustration,  however,  is  on  the  basis  of  a  hypo- 
thetical cell  (p.  216). 

A  list  of  immunizing  bodies,  their  anti-bodies, 
and  sjmonyms  for  complement  and  amboceptor, 
is  also  appended  (p.  217). 


IMMUNE   HUBHTAyCEH. 


217 


List  of  Immunizing  Bodies  and  Theie  Antibodies. 

Antigens  or  Products  of 
Immnnizing  immuniza- 
substances.  tion. 


List  of  Im- 
mune Sub- 
stances. 


Toxins. 

Complements 

Ferments. 

Precipitogen- 
o  u  s  s  ub  - 
stances 

Agglutinogen- 
o  us  s  ub - 
stances 

Opsinogenous 
substances 
of  bacteria 

Cytotoxin  pro- 
ducing sub- 
stances 


Precipitins 
Agglutinins 
Cytotoxins 

Hemolysins, 

etc. 


Complement 


Alexin 
Cytase 


Antitoxins. 
An  ticomple- 

ments 
Antiferments 
Precipitins 


Agglutinins 
Opsonins 
Cytotoxins.  . . 


Hemolysins 
Bacteriolysins 
Special    Cyto- 
toxins 
Spermotoxin 
Nephrotoxin 
Hepatotoxin 
Neurotoxin 
Syncytioly- 
sin,  etc. 


Consisting  o  f 
two  bodies, 
i.  e.,  comple- 
m  e  n  t  and 
amboceptor. 


Immunization  avith  Antibodies. 


Antiprecipitins 
Antiagglutinins  {1) 
Anticytotoxins 

Antihemolysins, 

etc. 


Consisting  either  of  anti- 
complements  or  antiam- 
boceptors ;  the  latter 
may  be  an  antibody  for 
the  complementophilous 
or  for  the  cytophilous 
haptophore  of  the  ambo- 
ceptor. 


Synontms. 

Amboceptor 

Immunk'Jrper 

Zwischenkorper 

Intermediary  body 

Substance  sensibilisatrice 

Fixator 

Preparator 

Copula 

Desmon 


CHAPTER  XVI. 


TEINCIPLES    OF    SERUM    THERAPY. 

In  the  strict  sense  serum  therapy  means  the  in- 
jection of  antitoxic  or  antibacterial  serums  for 
curative  or  prophykictic  purposes  ;■  this  is  passive 
immunization  or  direct  serum  therapy.  Active 
immunization,  in  which  the  tissues  of  the  individ- 
ual are  induced  to  form  antitoxins  or  antibacterial 
substances  as  a  result  of  vaccination  or  protective 
inoculations,  may  be  considered  as  indirect  serum 
therapy.  "We  may,  therefore,  include  thn  latter  as 
one  of  the  serotherapeutic  measures. 

Bearing  in  mind  the  significance  of  the  terms 
active  and  passive  immunization,  and  the  fact 
that  they  may  be  used  for  curative  and  prophylac- 
tic purposes,  the  various  procedures  may  be  classi- 
fied as  follows:* 

I.      PROPHYLACTIC    INJECTIONS. 

_  Classified-  A.  Active  immunization,  in  which  vaccina- 
therapeutic  tion  and  protective  inoculations  are  included,  as 
with  the  organisms  of  typhoid,  cholera  and  plague. 
Depending  on  the  material  injected,  the  result  is 
the  formation  of  antitoxins  or  antimicrobic  sub- 
stances (amboceptors)  ;  agglutinins  are  formed  in- 
cidentally. 

1.  Inoculation  of  virulent  organisms,  (a)  In- 
oculation with  small  amounts  of  a  virulent  organ- 
ism, i.  e.,  of  a  non-fatal  dose ;  used  principally  in 
experimental  work.     (&)  Inoculation  with  virulent 

•  Modified  from  Deutsch  and  Feistmantel  in  "Die 
Impfstofife    und    Heilsera,"    Leipsic.     Geo.    Tliieme,  1903. 


Measures. 


ACTIVE  IMMUNIZATION.  219 

organisms  into  a  tissue  which  has  some  natural  re- 
sistance. The  success  of  vaccination  against  small- 
pox by  using  virus  obtained  directly  from  the  dis- 
eased, a  method  which  was  practiced  in  earlier 
times,  was  probably  due  to  the  fact  that  the  virus 
found  unfavorable  conditions  for  the  development 
of  virulence  in  the  skin.  In  some  instances  im- 
munization is  accomplished  more  successfully  Ijy 
inoculation  of  bacteria  or  toxins  into  the  blood 
stream,  as  in  Kitt's  method  of  vaccination  against 
symptomatic  anthrax  and  in  immunization  with 
rattlesnake  venom.  . 

2.  Injection  of  attenuated  virus  or  toxin.  At- 
tenuation may  be  accomplished  by  air  and  light 
(chicken-cholera,  Pasteur)  ;  by  cultivation  at  high 
temperatures  (anthrax,  Pasteur)  ;  by  chemical 
agents  (anthrax,  Eoux;  diphtheria  and  tetanus 
toxins,  Behring  and  Eoux) ;  by  desiccation  (rabies, 
Pasteur)  ;  by  passing  the  virus  through  other 
animals  (swine  erysipelas,  Pasteur).  This  last 
observation  was  a  most  instructive  one;  passing 
the  bacillus  through  the  rabbit  several  times  in- 
creased its  virulence  for  the  rabbit  but  decreased  it 
for  swine,  while  passing  the  organism  through  the 
dove  increased  its  virulence  for  swine. 

3.  Injection  of  killed  organisms  (anthrax,  Tous- 
saint;  swine  plague,  Salmon  and  Smith).  This 
is  the  safest  means  of  vaccinating  against  cholera, 
typhoid  and  plague.  In  the  Pasteur  treatment  of 
hj^drophobia  the  first  injection  of  the  dried  spinal 
cord  probably  contains  the  Irilled  virus. 

4.  Injection  of  bacterial  constituents  (a)  Bacter- 
ial cell  plasm  (Buchner's  plasmin,  obtained  by  sub- 
mitting micro-organisms  to  high  pressure,  and 
Koch's    tuberculin    TE)  ;    (&)     Soluble    bacterial 


220  IXFECTIOX  AXD  IMMUXITY. 

products  (tlie  bacterial  proteins,  as  Koch's  old 
tuberclin  and  mallein ;  the  sohible  toxins ; 
products  of  bacterial  autolysis),  ^\^len  toxins 
are  injected  antitoxins  are  formed.  The 
autolytic  products  of  some  organisms,  e.  g., 
typhoid  and  dysentery,  cause  the  formation  of  bac- 
tericidal amboceptors  and  agglutinins,  but  not 
antitoxins. 

B.  Passive  immunization:  the  prophylactic  in- 
jection of  antibacterial  and  antitoxic  serums. 

C.  Mixed  active  and  passive  immunization:  the 
simultaneous  injection  of  an  immune  serum  with 
the  corresponding  organism,  which  may  be  killed 
or  living.  The  serum  causes  immediate,  though 
temporary,  resistance,  and,  in  the  meantime,  an 
active,  more  permanent  immunity  develops  as  a 
consequence  of  the  injection  of  the  organisms. 
This  method  has  been  practiced  with  swine  plague, 
swine  erysipelas,  rinderpest,  and  experimentally 
in  typhoid,  cholera  and  plague. 

II.       CURATIVE    IXJECTIONS. 

A.  Active  imnnmization. 

1.  Injection  of  killed  micro-organisms  in  small 
doses  with  the  intention  of  hastening  antibody  for- 
mation, as  suggested  by  Fraenkel  in  the  treatment 
of  typhoid  fever;  value  not  yet  demonstrated. 

B.  Passive  immunization. 

1.  With  antitoxic  serums :  diphtheria,  tetanus, 
snake  bites,  plague,  tuberculosis  (?),  t3'phoid  (?), 
streptococcus  infections  (?),  etc. 

2.  "With  antibacterial  serums :  typhoid,  cholera, 
plague,  dysentery,  streptococcus  (?),  staphylococ- 
cus (?)  and  pneumococcus  (?)  infections. 

In  general,  serums  to  be  effective  must  have  a 


ANTITOXIC  THERAPY.  221 

certain  strength.  When  diphtheria  antitoxin  was  General 
first  used  j)reparations  were  put  on  the  market  ofiierums. 
which  contained  twenty  or  fewer  antitoxin  units 
per  cubic  centimeter,  a  strength  which  would 
necessitate  the  injection  of  150  c.c.  or  more  in  or- 
der to  introduce  3,000  units.  Much  of  the  early 
criticism  of  dijDhtheria  antitoxin  is  traceable  to  the 
low  vahie  of  the  serums  used  at  that  time  rather 
than  to  an  injurious  effect  on  the  patients.  If 
diphtheria  antitoxin  now  contains  less  than  250 
units  per  c.c.  it  is  considered  unfit  for  use;  many 
serums  contain  500 -or  more  units  per  c.c. 

Antitoxic  and  other  serums  should  be  free  from 
micro-organisms  and  toxins.  The  cases  of  tetanus 
which  developed  in  St.  Louis  following  the  injec- 
tion of  diphtheria  antitoxin  will  be  remembered. 
With  correct  governmental  supervision  of  the 
manufacture  of  serums,  such  accidents  are  entirely 
preventable.'- 

For  the  sake  of  simplicity  we  may  consider  the 
principles  involved  in  serum  therapy  under  the 
three  topics  of  (a)  antitoxins,  (h)  bactericidal  or 
antibacterial  serums,  and  (c)  vaccination. 

(a)   antitoxins. 

It  has  been  sufficiently  emphasized  that  neutral-  Antitoxins. 
ization  of  toxin  by  antitoxin  implies  a  chemical 
union  between  the  two  substances.  When  the  two 
are  mixed  outside  the  body  at  a  given  temperature 
and  at  a  given  concentration,  the  rapidity  and  com- 
pleteness with  which  the  union  occurs  depends 
only  on  the  degree  of  affinity  which  one  has  for  the 
other.  There  is  no  third  substance  with  which  one 
or  the  other  may  unite.    In  the  body,  however,  the 

1.   See  appendix  to  Chapter  VII    (Part  I). 


22-2  JXFECriOX  AXD  IMMUXITY. 

conditions  are  more  complex;  in  this  case  two  com- 
binations are  possible  for  the  toxin,  one  with  the 
antitoxin  which  has  been  introduced  and  a  second 
with  the  tissue  cells.  As  an  instance  of  the  great 
rapidity  with  which  toxin  may  unite  with  cells, 
the  work  of  Heymans  with  tetanus  toxin  may  be 
cited.  ''Heymans  found  that,  if  all  the  blood  were 
removed  from  an  animal  a  few  minutes  after  the 
injection  of  a  single  fatal  dose  of  tetanus  toxin 
and  the  blood  of  another  animal  substituted,  still 
the  animal  died  of  tetanus"  (Eitchie) ;  that  is  to 
say,  all  the  toxin  had  been  bound  by  the  cells  in 
that  brief  time. 
Binding  of  Other  experiments  show  that  quantities  of  toxin 
Tissues',  '^i^tl  antitoxin  which  are  neutral  when  mixed  be- 
fore injection  are  not  entirely  neutral  if  injected 
separately  and  at  difEerent  points  of  the  body.  In 
this  instance  some  of  the  toxin  has  had  time  to 
unite  with  tissue  cells  before  it  could  come  in  con- 
tact with  the  antitoxin. 

Certain  work  by  Donitz  illustrates  not  only  the 
rapidity  with  which  toxin  may  be  bound  by  the 
tissue,  but  also  the  method  by  which  antitoxin  ef- 
fects a  cure.  In  relation  to  tetanus  he  found  that 
if  the  toxin  were  injected  first  and  the  antitoxin 
four  minutes  later,  a  quantity  of  antitoxin,  which 
was  slightly  in  excess  of  the  neutralizing  dose,  was 
required  to  prevent  the  development  of  tetanic 
s}Tnptoms;  if  he  waited  eight  minutes,  six  times 
as  much  antitoxin;  after  sixteen  minutes,  twelve 
times  as  much;  after  one  hour,  twenty-four  times 
the  simple  neutralizing  dose  was  required.  A  few 
hours  later  no  amount  of  antitoxin  could  save  the 
animal.  Similar  conditions  were  met  in  the  neu- 
tralization of  diphtheria  toxin  by  its  antitoxin  in 


CURATIVE  ACTION.  223 

the  body.  Madsen,  in  performing  what  he  called 
"Curative  Experiments  in  the  Keagent  Glass/' 
found  that  the  longer  tetanolysin  had  been  in  con- 
tact with  erythrocytes^,  the  more  antitetanolysin 
was  required  to  tear  away  the  toxin  from  the  cor- 
puscles. Practical  experience  with  diphtheria  also 
indicates  that  the  longer  the  disease  lasts  the  more 
antitoxin  is  required  for  cure. 

The  experiments  just  cited  give  us  a  clear  con-  Nature  of 
ception  as  to  what  is  meant  by  the  curative  action  Actiotll 
of  an  antitoxin — an  action  which  consists  not  of 
the  neutralization  of  the  circulating  toxin,  but  of 
the  wresting  away  from  the  tissue  of  the  toxin 
which  has  been  bound.  Incidentally  the  circulat- 
ing toxin  is  neutralized,  and  for  this  step,  which 
is  essentially  prophylactic  in  nature,  the  simple 
equivalent  of  antitoxin  is  required.  But  for  the 
wresting  of  toxin  from  tissue  cells  not  a  mere 
equivalent  of  antitoxin,  but  a  great  excess,  is  re- 
quired, as  shown  by  the  experiments  of  Donitz  and 
of  Madsen. 

When  diphtheria  or  tetanus  has  advanced  so  far 
that  no  amount  of  antitoxin  will  effect  a  cure,  the 
relation  of  the  toxin  to  the  cells  has  become  some- 
thing more  than  mere  chemical  union.  Further 
processes  of  a  biologic  or  biochemic  nature  have  set 
in  in  which  the  toxin  may  have  .become  an  integral 
part  of  the  protoplasm,  and  the  toxophorous  group 
may  have  begun  its  destructive  action,  whatever 
the  nature  of  this  action  may  be. 

It  is  important  to  recognize  that  antitoxin  can 
not  repair  an  injury  already  done  by  the  toxin. 
The  repair  of  the  injury  depends  on  the  recupera- 
tive power  of  the  cells;  hence,  antitoxin  cures  by 
tearing  from  the  cells,  perhaps  not  all,  but  so  much 


224 


iXFi:cTioy  Axij  immuxity. 


l\so  Important 
Principles. 


Tetanus. 


of  tlio  toxin  that  lo.<s  tlum  a  fatal  dose  remains  in 
the  celL 

Wo  may  learn  from  the  experiments  of  Donitz 
antl  of  Madsen  two  important  principles  of  anti- 
toxic therapy:  First,  that  of  early  administration, 
i.  e.,  before  a  fatal  amount  of  toxin  has  been 
bound,  and,  second,  the  necessity  of  injecting  suffi- 
cient quantities  of  antitoxin. 

The  comparative  study  of  diphtheria  and  tet- 
anus has  clarified  the  principles  of  antitoxic 
tlicrapy  to  no  small  degree.  Knowing  that  diph- 
theria antitoxin  has  a  much  greater  curative  value 
than  tetanus  antitoxin,  we  find  some  conditions 
which  would  seem  to  explain  the  difference,  at 
least  in  part. 

In  regard,  to  tetanus  we  have  the  following 
facts:  In  the  test-glass  the  affinity  between  the 
toxin  and  antitoxin  is  rather  weak,  since  approxi- 
mately forty  minutes  are  required  for  complete 
neutralization  (Ehrlich).  On  the  other  hand,  the 
experiments  of  Donitz  and  of  Heymans  show  that 
the  affinity  of  the  toxin  for  nervous  tissue  is  ex- 
ceedingly strong,  all  the  toxin  being  taken  up 
within  a  few  minutes.  These  two  conditions  alone 
suggest  the  probability  of  a  low  curative  value  on 
the  part  of  the  serum.  The  toxin  of  tetanus  also 
has  a  remarkable  selective  action  on  the  most  vital 
of  all  organs,  the  central  nervous  system;  hence,  a 
lower  grade  of  injury  may  prove  fatal  than  in 
other  infections  in  which  less  important  organs  or 
those  of  greater  recuperative  power  are  involved 
chiefly.  Furthermore,  it  seems  (Meyer  and  Ean- 
som,  Marie  and  Morax)  that  the  tetanus  toxin  is 
taken  up  by  the  nerve  endings  and  reaches  the 
ganglionic   cells   by   way    of   the   axis    cylinders. 


PRINCIPLEH.  225 

whereas  the  antitoxin  which  is  injected  remains 
chiefly  in  the  blood  and  lymphatic  circulations. 
Hence,  the  toxin,  to  a  certain  extent,  is  isolated 
and  less  accessible  to  the  action  of  the  antitoxin. 

Concerning  diphtheria,  the  affinity  between  Diphtheria. 
toxin  and  antitoxin  is  relatively  strong,  for  com- 
plete neutralization  in  the  test-glass  takes  place  in 
about  fifteen  minutes  (Ehrlich).  On  the  other 
hand,  clinical  experience  indicates  that  the  affinity 
of  diphtheria  toxin  for  tissue  cells  is  less  than  that 
of  tetanus  toxin,  for  diphtheria  may  readily  be 
cured  on  the  second  or  third  day  of  the  disease, 
whereas  a  cure  of  tetanus  is  rarely  affected.  These 
would  seem  to  be  favorable  conditions  for  success- 
ful serum  therapy.  Although  the  toxin  of  diph- 
theria may  attack  the  nervous  system,  the  paraly- 
sis seen  in  such  cases  is  seldom  fatal.  On  the  basis 
of  anatomic  findings  in  fatal  cases  it  seems  prob- 
able that  the  greater  portion  of  the  toxin  is  taken 
up  by  parenchymatous  and  lymphatic  organs,  and 
by  connective  tissues  (animal  experiments),  which 
compared  with  the  nervous  tissue  are  of  less  imme- 
diate importance  for  life  and  have  greater  recuper- 
ative powers.  We  may  infer  from  clinical  experi- 
ence that  diphtheria  toxin  is  so  situated  in  the 
body  that  it  is  accessible  to  the  action  of  the  anti- 
toxin. 

We  have,  therefore,  the  following  factors  important 
which  apparently  are  of  importance  for  the  sue-  forSuccess 
cess  of  antitoxic  therapy:  1.  The  concentration 
(strength)  of  the  antitoxin  which  is  injected.  2. 
Its  freedom  from  contamination  and  adventitious 
'toxins.  3.  The  time  of  its  administration.  4.  The 
quantity  injected.  5.  The  degree  of  affinity  be- 
tween toxin  and  antitoxin.  6.  The  degree  of  affinity 


220  IXFECriOy  AND  IMMUMTY. 

.  between  toxin  and  tissue  cells.  7.  The  amount  of 
toxin  -which  may  be  bound  without  a  fatal  issue,  of 
whicli  the  vital  importance  of  the  organs  involved 
and  their  recuperative  powers  are  factors.  8.  The 
location  of  the  toxin  in  the  body,  i.  e.,  its  accessi- 
bility for  the  antitoxin. 
Prophylactic  What  has  bccn  said  relates  to  the  curative  ac- 
Antltoxinl  tion  of  antitoxin.  It  is  evident  that  the  action  of 
antitoxin,  when  used  as  a  prophylactic,  is  of  a 
simpler  nature,  for  in  this  instance  the  conditions 
approximate  those  of  the  test-tube  experiment. 
There  has  been  opportunity  for  the  antitoxin  to 
become  uniformly  distributed  in  the  blood  and 
lymphatic  circulations;  hence,  it  is  able  to  meet 
and  to  bind  the  toxin  before  the  latter  comes  in 
contact  with  the  receptors  of  important  cells.  The 
high  value  of  tetanus  antitoxin  as  a  prophylactic, 
a  value  -which  has  become  e\ident  in  recent  years, 
probably  depends  on  this  condition. 

The  immunity  wdiich  is  afforded  by  a  prophy- 
lactic injection  of  antitoxin  is  of  short  duration, 
from  t-R^o  to  three  -weeks;  the  antitoxin  is  excreted 
in  the  urine  to  a  considerable  extent,  but  in  part 
may  be  bound  and  assimilated  by  the  tissues. 

(b)  bactericidal  or  an'tibactericidal  serums. 

Bactericidal  Attention  has  been  directed  repeatedly  to  a 
large  group  of  organisms  the  toxic  constituents  of 
which  are  integrally  associated  with  the  proto- 
plasm of  the  microbes;  the  toxic  substances  are 
endotoxins.  Certain  members  of  this  group,  of 
-u^hich  the  typhoid,  paratyphoid,  colon  and  dysen- 
tery bacilli  and  the  vibrio  of  cholera  are  represent- 
atives, cause  the  development  of  strong  bacterici- 
dal serums  in  the  immunized  animal.    In  Chapter 


Serums. 


A  N  TIB  A  V  TJJIilAL  HE  It  UMH. 


227 


Xll,  K,  it  was  shown  that  such  serums  have  no 
power  of  neutralizing  the  endotoxins  of  the  corre- 
sponding organisms;  hence,  whatever  prophylactic 
and  curative  properties  they  may  have  would  seem 
to  depend  on  the  bactericidal  action  of  the  ambo- 
ceptor-complement  complex.  As  to  whether  the 
substances  which  stimulate  phagocytosis,  i.  e.,  the 
opsonic  or  bacteriotropic  substances  are  of  impor- 
tance for  the  intra  vitam  action  of  bactericidal 
serums,  remains  to  be  definitely  established. 

It  is  common  knowledge  that  bactericidal 
serums  have  not  been  successful  curative  agents, 
although  in  test-glass  experiments  they  may  be 
able  to  kill  large  numbers  of  organisms.  Experi- 
mental work  has  brought  to  light  a  number  of  con- 
ditions which  render  their  inefEectiveness  some- 
what intelligible,  but  this  knowledge  has  been  of 
little  service  in  increasing  their  value,  and  at  this 
moment  their  outlook  as  curative  agents  is  not  very 
encouraging. 

Animal  experiments  indicate  that,  prophylacti- 
cally,  they  are  much  more  powerful  than  when 
used  as  curative  agents.  Unfortunately,  however, 
as  in  the  case  of  antitoxins,  the  immunity  which  is 
conferred  is  of  short  duration,  the  serum  being  ex- 
creted or  the  antibodies  destroyed  within  two  or 
three  weeks.  For  this  reason  they  are  not  suited 
for  general  prophylactic  use  in  man,  but  they  may 
be  distinctly  useful  when  combined  with  vaccina- 
tion, as  indicated  later. 

Bactericidal  serums  are  efficient  in  saving  ex- 
periment animals,  provided  the  serum  is  injected 
in  advance  of,  simultaneously  with  or  very  shortlv 
after  the  bacteria  are  introduced.  By  injecting 
the  vibrio  of  cholera  and  anticholera  serum  simul- 


Curative  and 
Prophylactic 
Power. 


Time  of 
injection. 


22S  IXFECTIOy  AXD  IMMUyiTY. 

tancously  one  may  readily  save  a  guinea-pig  from 
ten  times  the  fatal  dose,  or  more.  If  the  culture 
be  injected  first  and  the  serum  later  a  larger 
amount  of  serum  is  required  to  save  the  animal. 
After  a  few  hours  a  sutlicient  amount  of  serum  to 
kill  all  tlie  vibrios  may  be  injected,  yet  the  ani- 
mal will  die  from  the  action  of  the  endotoxins 
which  have  been  liberated.  The  organisms  had 
proliferated  to  such  an  extent  that  the  mass, 
though  dead,  contained  a  fatal  amount  of  endo- 
toxin. A  statement  made  previously  may  be  re- 
peated, that  the  administration  of  a  bactericidal 
serum  rather  than  being  beneficial  may  actually  be 
injurious,  in  that  it  dissolves  the  micro-organisms 
rapidly,  an  excessive  amount  of  endotoxin  thereby 
liberating;  this,  perhaps,  is  not  definitely  estab- 
lished as  a  point  of  practical  importance. 

Having  determined  the  amount  of  a  bactericidal 
serum  which  is  able  to  save  a  guinea-pig  from  an 
incipient  infection,  one  may  calculate  on  the  basis 
of  weight  the  amount  which  would  be  required  to 
save  a  man  under  the  same  conditions;  frequently 
it  amounts  to  impossible  quantities,  hundreds  of 
cubic  centimeters.  The  conditions  are  all  the  less 
promising  when  we  remember  that  physicians  are 
usually  called  on  to  treat  well-established  rather 
than  incipient  infections. 
Peculiarities  of  Other  conditions  which  operate  against  the  ef- 
^and'Ambo-  fectivencss  of  bactericidal  serums  as  curative 
agents  have  to  do  with  peculiarities  of  comple- 
ments and  amboceptors.  The  lability  of  comple- 
ment involves  certain  difficulties.  A  bactericidal 
serum,  as  one  would  purchase  it,  contains  none, 
because  of  its  spontaneous  degeneration.  Theo- 
retically, this  difficulty  may  be  obviated  in  three 


ceptors. 


SUITABLE   COMPLEMENT.  229 

ways:  First,  one  may  use  serums  which  are  fresh 
from  the  immunized  animal ;  second,  one  may  com- 
plement the  solution  of  amboceptors  (old  immune 
serum)  by  the  addition  of  fresh  serum  from  a  nor- 
mal animal  which  is  known  to  contain  suitable 
complement;  or,  third,  one  may  inject  the  comple- 
ment-free serum  and  place  reliance  on  the  comple- 
ment which  exists  in  the  plasma  and  lymph  of  the 
patient  for  activation  of  the  amboceptors.  It  is 
sufficiently  established  that  none  of  these  proce- 
dures enhances  the  curative  value  of  the  serums  to 
a  satisfactory  extent. 

Eegardless  of  the  amount  of  foreign  comple-  Absorption 
ment  which  is  introduced,  it  appears  to  be  di-  by  the  Tissues! 
verted  from  its  function.  It  has  been  shown  ex- 
perimentally that  the  tissues  may  absorb  a  foreign 
complement,  and  the  mere  fact  that  anticomple- 
ments  are  formed  so  readily  indicates  that  comple- 
ment may  be  bound  by  the  tissues.  In  accordance 
with  a  rather  general  principle,  if  the  animal 
which  furnishes  the  serum  is  remote  from  man 
zoologically  there  is  all  the  more  likelihood  of  the 
complement  being  fixed  by  human  tissues. 

It  has  been  suggested  that  if  one  should  choose  choice  of 
for  immunization  animals  which  are  closely  re-  imlUlfni^zation. 
lated  to  man,  as  chimpanzees  and  monkeys,  a 
double  advantage  would  be  gained :  First,  the  for- 
eign complement  may  be  identical  or  similar  to 
that  in  man  and  consequently  would  be  less  likely 
to  be  absorbed  by  the  tissues;  and,  second,  the 
complementophilous  haptophores  of  the  ambocep- 
tors may  be  so  constructed  that  human  comple- 
ment would  serve  for  activation.  Theoretically, 
the  conditions  would  be  ideal  if  immune  human 
serum  were  available  for  therapeutic  purposes. 


Complement. 


230  IXFECTIOX  AXD  lAlMUMTY. 

If  one  depends  on  the  complement  in  the  pa- 
tient's body  for  activation  of  the  amboceptors, 
there  are  two  possible  difliciilties  of  importance : 
First,  the  native  complement  of  the  body  is  often 
decreased  during  infections  and  in  some  chronic 
diseases  and  may  be  too  little  for  thorough  activa- 
tion; second,  the  amboceptors  of  the  immune 
serum  may  demand  for  their  activation  a  comple- 
ment or  complements  which  the  body  does  not  con- 
tain. 
Diversion  of  Divcrsiou  of  Complement  has  been  referred  to  as 
a  phenomenon  seen  in  test-tube  experiments.  In 
this  condition  an  excess  of  amboceptors  in  some 
way  decreases  the  power  of  the  serum;  by  an  ex- 
cess of  amboceptors  one  means,  in  this  instance, 
such  a  quantity  that  many  are  unbound  by  the 
bacteria.  It  is  supposed  that  a  certain  amount  of 
the  complement  is  absorbed  by  free  or  unbound' 
amboceptors,  hence  the  effect  is  like  that  of  too 
little  complement.  In  the  desire  to  administer  a 
sufficient  amount  of  antibodies,  so  much  may  be 
introduced  that  diversion  of  the  complement  oc- 
curs in  the  body.  Results  obtained  by  Loffler  and 
Able,  by  Pfeiffer  and  by  Buxton  and  others,  in 
which  excessive  doses  of  immune  serum  were  less 
protective  than  moderate  doses,  show  that  a  simi- 
lar phenomenon  occurs  in  the  body. 
Inaccessibility  In  Certain  diseases  the  microbes  are  so  situated 
that  a  serum  as  ordinarily  administered  may  not 
be  able  to  reach  them.  Pfeiffer  thinks  that  there 
is  little  hope  for  the  serum  treatment  of  cholera 
because  of  the  exclusive  location  of  the  living  or- 
ganisms in  the  intestinal  tract.  In  typhoid  also 
the  intestines  are  a  reservoir  of  typhoid  bacilli, 
although  the  living  organisms  reach  the  circula- 
tion in  abundance. 


of  Microbes. 


SUMMARY.  231 

By  way  of  summary,  the  following  conditions 
appear  as  factors  in  the  low  curative  value  of  bac- 
tericidal serums:  1.  Bactericidal  serums  are  not 
antitoxic.  2.  They  may  liberate  an  excessive 
amount  of  endotoxin  by  dissolving  the  bacteria.  3. 
The  lability  of  exogenous  complement.  4.  The 
power  of  the  tissues  to  absorb  the  complements  of 
a  foreign  serum.  5,  The  lack  of  a  sufficient 
amount  of  suitable  complement  in  the  human 
body.  6.  The  difficulty  of  obtaining  amboceptors 
for  which  human  complements  are  suited.  7.  The 
possibility  of  diversion  of  complement  by  an  ex- 
cess of  amboceptors.  8.  Inaccessibility  of  the 
micro-organisms  in  certain  infections  (cholera, 
typhoid). 

As  pointed  out  elsewhere,  another  group  of  or-  other ''Anti- 
ganisms,  the  members  of  which  contain  endo-  serums' 
toxins,  causes  the  formation  neither  of  antitoxins 
nor  of  bactericidal  serums;  streptococcus,  staphy- 
lococcus, pneumococcus,  etc.  Many  investigators, 
nevertheless,  are  positive  in  their  claims  that  the 
antiserums  for  these  organisms  have  a  protective 
and  even  a  curative  value.  The  properties  on  which 
their  value  depends  have  not  been  satisfactorily 
ascertained.  Although  certain  antistreptococcus 
serums  are  said  to  be  antitoxic,  it  is  contended  bj 
others  that  they  act  by  simulating  phagocytosis. 
Work  now  in  progress  promises  to  show  that  im- 
munization with  these  organisms  causes  an  in- 
crease in  the  opsonins.  Their  curative  value  is 
very  low  in  experimental  work  and  they  fail  totally 
if  injected  a  few  hours  subsequent  to  the  introduc- 
tion of  the  organisms.  Clinically,  we  are  familiar 
with  them  as  failures. 

It  is  particularly  in  relation  to  the  streptococ-  ■ 


232  lyFECTlOX  AXD  IMML'MTY. 

.  cus  tliat  the  so-called  polyvalent  serums  have  been 
prepared.  Cultures  of  streptococcus  obtained 
from  numerous  sources  are  used  in  the  immuniza- 
tion with  the  expectation  that  the  serum  will  be 
effective  against  various  strains  of  streptococci. 
The  principle  may  be  an  important  one  in  the 
preparation  of  other  antibacterial  and  bactericidal 
serums. 

(C)    VACCINATION^. 

Vaccination  or  We  are  most  familiar  with  the  terms  vaccine 
'"'"ocuVatlon!  and  vaccination  as  applied  to  protective  inocula- 
tion against  smallpox.  They  are  used,  however, 
with  equal  propriety  in  all  instances  in  which  the 
attenuated  or  killed  virus  of  a  disease  is  inoculated 
for  the  purpose  of  establishing  resistance  to  an 
infection.  The  process  set  in  motion  by  vaccina- 
tion is  one  of  active  immunization  in  which  the 
cells  are  induced  to  form  specific  antibodies  over  a 
long  period;  hence,  the  resistance  is  more  pro- 
tracted than  tliat  established  by  passive  immuni- 
zation. 

Certain  experimental  work,  as  previously  stated, 
indicates  that  the  acquired  resistance  persists  after 
the  formation  of  antibodies  has  ceased,  even  after 
the  quantity  of  the  latter  has  sunk  to  the  normal. 
This  condition  has  been  explained  by  assuming 
that,  as  a  consequence  of  vaccination,  the  cells  of 
the  body  have  been  "trained"  to  produce  the  cor- 
responding receptors;  hence,  when  the  micro-or- 
ganisms gain  entrance  at  a  subsequent  time  new 
antibodies  are  formed  so  rapidly  and  in  such  abun- 
dance that  the  incipient  infection  is  overcome. 

In  some  instances  the  nature  of  the  virus  used 
is  unknovm,  as  in  smallpox  and  hydrophobia;  in 
all  probability,  however,   it  consists   of  micro-or- 


VACCINATION.  233 

ganisms  rather  than  of  toxins  alone.  In  the  case 
of  typhoid,  cholera,  plague  and  other  diseases  of 
known  etiology  pure  cultures,  living  or  killed,  are 
inoculated.  Protection  does  not  follow  immedi- 
ately on  the  inoculation.  We  are  sufficiently  fa- 
miliar with  this  fact  in  relation  to  smallpox,  in 
which  several  days  are  required  for  the  formation 
of  a  protective  amount  of  the  antibodies.  There 
is  reason  to  believe  that  the  interval  between  the 
inoculation  and  the  appearance  of  antibodies  is 
characterized  by  a  decreased  resistance  on  the  part 
of  the  individual,  so  that  during  this  brief  period 
he  is  unusually  susceptible  to  infection. 

That  period  immediately  following  the  injec-  Negative  and 
tion  of  a  toxin  or  microbe,  in  which  the  quantity  phases? 
of  antibodies  undergoes  a  temporary  decrease, 
Wright  speaks  of  as  the  negative  phase  of  the  im- 
munization; whereas  that  period  marked  by  the 
new  formation  of  antibodies  is  called  the  positive 
phase.  The  negative  phase  lasts  from  a  day  or 
two  to  several  days,  depending  on  the  quantity  and 
nature  of  the  virus  injected  (typhoid).  A  second 
injection  should  not  be  given  during  the  negative 
phase,  since  it  causes  a  further  decrease  in  the 
antibodies  and  prolongs  the  phase.  Wright  speaks 
of  this  as  a  cumulative  negative  phase.  A  cumu- 
lative positive  phase,  marked  by  the  formation  of 
larger  amounts  of  antibodies,  may  be  induced  by 
the  proper  spacing  of  a  number  of  injections. 

In   certain   instances   the   nature   of   the    anti-  Nature  of 
bodies  is  known.    In  t5rphoid,  cholera,  plague  and  ^"*''""*'^- 
dysentery,  for  example,  they  consist  of  bactericidal 
amboceptors;     agglutinins     and     precipitins     are 
formed  incidentally.     The  amboceptors  naturally 
depend  on  the  complement  of  the  body  for  their 


234  INFECTION  AND  IMMLMTY. 

activation.  If  the  disease  is  one  of  unknown  etiol- 
ogy the  nature  of  the  antibodies  is  not  easily  de- 
termined. "We  should  keep  in  mind  the  possibil- 
ity that  vaccination  may  cause  an  increase  of  the 
opsonins  and  that  the  potential  phagocytosis  may 
thereby  become  greater. 

In  case  the  incubation  period  of  the  vaccination 
is  shorter  than  that  of  tlie  disease  (smallpox,  hy- 
drophobia) vaccination  usually  is  successful  even  if 
practiced  within  a  limited  time  after  exposure  to 
infection. 

Vaccination  in  individual  diseases  is  considered 
in  Part  II  (see  also  Chapter  VJ,  pp.  57,  58). 

Theoretically  it  would  be  possible  to  immunize 
man  against  diphtheria  and  tetanus  by  inoculating 
with  small  amounts  of  the  corresponding  toxins. 
Such  a  procedure,  for  obvious  reasons,  would  be 
unnecessary  and  unjustifiable. 
Mixed  Active  It  is  not  iinlikely  that  mixed  active  and  passive 
immunization  will  be  of  great  service  in  some  in- 
fections. A  successful  campaign  against  rinder- 
pest has  been  carried  on  in  the  Philippines  by  this 
method.  The  blood  of  infected  cattle  contains  the 
virus,  which  as  yet  has  not  been  cultivated  artifi- 
cially. The  serum  of  cattle  which  have  recovered 
from  the  disease,  or  which  have  been  immunized 
cautiously  with  infected  blood,  contains  the  speci- 
fic antibodies.  Both  the  immune  serum  and  viru- 
lent blood  are  used  for  the  inoculations.  The  same 
principle  has  been  found  efl:ective  in  experimental 
work  with  cholera,  t5'phoid  and  plague.  Immedi- 
ate immunity  is  established  by  the  serum,  which 
would  eliminate  the  danger  period  mentioned 
above,  and  before  the  serum  disappears  entirely 
active  immunity  develops. 


and   Passive 
Immunization, 


PART   TWO-SPECIAL. 


Although  a  consistent  classification  of  the  infec- 
tious diseases,  on  the  basis  of  immunity,  is  impos- 
sible at  the  present  time,  a  certain  grouping  is  de- 
sirable for  the  sake  of  convenience.  The  following 
arrangement  of  those  diseases  we  are  able  to  con- 
sider is  made  on  a  basis  which  is  partly  etiologie, 
partly  with  reference  to  the  pathogenic  properties 
of  the  micro-organisms,  and  partly  to  the  nature 
of  the  reactions  excited  in  the  body  by  infection  or 
immunization.  In  some  instances  nothing  more 
than  general  analogies  suggest  themselves  as  a 
basis  for  the  grouping,  which  is  necessarily  provi- 
sional and  imperfect. 

GROUP  1. 

Diseases,  natural  or  experimental,  which  are 
caused  by  soluble  toxins  of  bacterial,  animal  or 
plant  origin.  Infection  or  immunization  induces 
immu.nity  to  subsequent  attacks  (except  in  hay  fe- 
ver), the  immunity  being  characterized  by  the 
formation  of  serum  antitoxins,  and  occasionally  of 
bacteriolysins  and  agglutinins.  The  serums  of 
highly  immunized  animals  are  protective  and  cur- 
ative for  the  corresponding  intoxications  in  man 
and  other  animals. 

A.    BACTERIAL  DISEASES. 
I.   DIPHTHERIA. 

Bacillus  diphtherice,  or  the  TvJebs-Loeffler  bacil- 
lus, was  discovered  by  Klebs  in  1883,  and  more 
fully  described  by  Loeffler  in  1884.    It  answers  all 


23G  INFECTION  AND  IMMUNITY. 


Characteris- 
tics of  the 


KoclTs  laws  in  its  relationsliip  to  the  cliseasc  of 
orflanism!  diiilitlieria.  It  is  a  non-niotilo,  rod-shaped  organ- 
ism having  about  the  length  of  the  tubercle  bacil- 
lus, but  twice  its  thickness.  One  end  commonly 
presents  a  flask-like  enlargement.  It  stains  by 
Gram's  method,  with  the  ordinary  anilin  dyes,  and 
with  the  special  stain  of  Xeisser  shows  a  peculiar 
granulation,  the  granules  of  Babes-Ernst.  It  is 
readily  cultivated,  especially  on  solid  media  which 
contain  serum  and  in  various  bouillons.  It  tends 
to  grow  in  coherent  masses  and  under  the  micro- 
scope the  cells  often  show  a  characteristic  phalanx- 
like arrangement. 

The  diphtheria  bacillus  is  an  obligate  parasite 
having  no  vegetative  existence  outside  of  the  body, 
is  very  resistant  to  desiccation  and  may  remain 
virulent  in  a  dried  state  for  from  one  to  five 
months.  Its  life  in  water  varies  from  a  few  days 
to  several  weeks,  having  its  shortest  existence  in 
distilled  water  and  its  longest  in  hydrant  water 
which  has  been  boiled.  It  disappears  more  quickly 
from  unboiled  hydrant  water.  It  is  very  suscepti- 
ble to  ordinary  antiseptics,  being  killed  in  a  few 
minutes  by  corrosive  sublimate  even  in  a  dilution 
of  1  to  10',000. 
Metiiodsof  The  sources  of  infection  may  be  enumerated  as 
follows:  1.  From  the  false  membranes,  sputum 
or  excretions  of  the  mouth,  pharynx,  nose,  con- 
junctiva and  deeper  respiratory  passages  of  in- 
fected individuals.  2.  From  convalescents  and 
those  who  have  fully  recovered,  even  after  serum 
treatment.  Virulent  organisms  may  persist  in  the 
pharynx  or  nose  of  convalescents  for  weeks  and 
months,  as  in  one  of  Prip's  cases  in  which  they 
were  found  twenty-two  months  after  recovery.     3. 


DIFHTHERIA..  237 

From  the  upper  air  passages  of  healthy  persons 
who  may  never  have  had  diphtheria,  but  who  have 
been  in  direct  or  indirect  contact  with  the  dis- 
eased. Kober  obtained  virulent  bacilli  from  8  per 
cent,  of  the  individuals  who  had  been  in  direct 
contact  with  patients,  and  he  states  that  0.83  per 
cent,  of  the  people  at  large  carry  with  them  viru- 
lent organisms.  This  condition  may  well  account 
for  the  "spontaneous"  origin  of  diphtheria  in  the 
susceptible.  4.  From  cases  of  latent  diphtheria  as 
represented  by  chronic  pharyngeal  diphtheria  and 
chronic  rhinitis  fibrinosa. 

Hence,  infection  takes  place  chiefly  by  direct 
contact,  but  frequently  also  by  indirect  contact. 
Transmission  by  kissing  or  by  other  means  of  inti- 
mate contact,  by  using  infected  cups  or  toys,  is 
well  recognized.  "Drop  infection,"  i.  e.,  from  in- 
fected globules  of  mucus  or  saliva  which  the  pa- 
tient emits  when  speaking  or  coughing,  may  occur, 
but  perhaps  is  not  of  great  significance.  The  same 
probably  is  true  of  "dust  infection,"  although,  as 
stated,  the  organism  may  remain  living  and  viru- 
lent in  a  dried  state  for  a  long  time.  The  disease 
is  rarely  transmitted  from  animals  to  man,  al- 
though such  transmission  may  occur  from  the  cat, 
which  occasionally  suffers  from  true  diphtheria. 
The  diphtheria  of  fowls  is  due  to  another  organ- 
ism. 

The  upper  air  passages,  more  rarely  the  conjunc- 
tiva, wounds  and  the  vulva,  are  recognized  as  in- 
fection atria. 

The  local  and  general  phenomena  of  diphtheria 
are  caused  by  the  soluble  toxin  which  the  organ- 
ism secretes.  Although  the  toxin  is  not  absorbed 
through,  nor  does  it  injure  the  unbroken  skin,  it 


Pathogenesis. 


238  IXFECTIOX  AND  IMilUNirY. 

•  produces  necrosis  of  the  mucous  surfaces  and  un- 
derlying tissue  at  the  site  of  infection.  Through 
the  wounded  surface  iibrin-forming  elements  es- 
cape, as  a  consequence  of  which  successive  laj^ers 
of  fibrin  are  deposited  and  the  fibrin,  together  with 
the  necrotic  surface,  leucocytes  and  associated 
micro-organisms  constitute  the  membrane  which 
so  often  marks  the  disease  clinically.  The  local 
process  is  similar  in  diphtheria  of  cutaneous 
wounds.  The  toxin  becomes  generalized  by  absorp- 
tion through  the  lymphatic  circulation. 
Localization  of  Characteristically  the  bacilli  are  confined  to  the 
theBaci  i.  ^-^.^  ^^  infection.  Although  diphtheritic  bacterie- 
mia  rarely  occurs,  the  bacilli  have  been  found  oc- 
casionally in  the  blood  and  viscera  of  fatal  cases. 

The  clinical  and  anatomic  conditions  lead  us  to 
believe  that  the  parench^Tnatous  organs,  the  lym- 
phatic tissues  and  the  cells  of  the  nervous  system 
contain  receptors  with  which  the  toxin  unites,  in- 
asmuch as  these  tissues  suffer  demonstrable  injury 
during  the  disease.  When  the  toxin  is  injected 
subcutaneously  into  animals,  localized  edema  and 
necrosis  occur;  hence,  the  connective  tissues  may 
also  take  up  a  portion  of  the  toxin,  diverting  it,  so 
to  say,  from  the  more  vital  organs. 

Mixed  Mixed  infections  render  diphtheria,  a  more  dan- 
infections.  ggj.Q^g  disease.  According  to  Baumgarten,  the 
streptococcus  is  associated  with  the  diphtheria  ba- 
cillus in  most  cases  of  diphtheria.  The  observa- 
tion of  Eoux  and  Yersin  that  the  streptococcus  in- 
creases the  virulence  of  the  diphtheria  bacillus 
both  in  the  test-tube  and  in  animal  experiments 
may  explain  to  some  degree  the  severity  of  the  dis- 
ease when  accompanied  by  streptococcus  infection. 
Aside  from  the  local  influence  of  the  streptococcus. 


DirilTUERIA.  239 

however,  a  general  invasion  by  this  organism  may 
occur,  with  such  consequences  as  acute  nephritis 
or  lobular  pneumonia,  and  in  this  condition  the 
diphtheritic  infection  may  fall  into  the  back- 
ground in  importance  (septic  diphtheria).  Post- 
diphtheritic suppurations  commonly  are  caused  by 
the  pyogenic  cocci,  but  sometimes  in  association 
with  the  diphtheria  bacillus  itself.  Earely  the 
bacillus  is  found  in  pure  culture  in  lobular  pneu- 
monia, a  condition  which  Plexner  and  Anderson 
produced  experimentally  in  animals.  In  puer- 
peral infections  with  the  streptococcus  a  puerperal 
diphtheria  is  sometimes  superimposed. 

Very  young  children  resist  diphtheritic  infec-  immunity  and 
tion.  A  certain  degree  of  immunity  may  be  trans-  "*""  '  "  ^" 
mitted  by  the  mother.  Observations  on  animals 
show  that  when  the  blood  and  milk  of  the  mother 
contain  antitoxin,  the  offspring  acquires  some  pro- 
tection, which,  however,  may  disappear  after  the 
cessation  of  nursing.  Polano  claims  that  anti- 
toxin passes  from  the  mother  to  the  child  through 
the  placenta.  From  the  second  to  the  seventh  or 
eighth  year  children  usually  are  very  susceptible. 
This  susceptibility  is  not  uniform,  however,  for 
many  children  escape  infection,  whereas  others, 
under  the  same  conditions,  contract  the  disease. 
Following  this  period  susceptibility  decreases  and 
after  the  fifteenth  year  the  disease  is  relatively 
rare. 

The  cause  of  the  immunity  which  develops  in 
the  absence  of  a  preceding  infection  has  not  been 
sufficiently  investigated.  In  some  cases  consid- 
erable amounts  of  antitoxin  are  found  in  the 
serum,  perhaps  enough  to  account  for  the  immun- 
ity.     The   prolonged   presence    of   bacilli    of   low 


Immunity. 


240  IXFECTIOX  AND  IMMUNITY. 

virulence  in  the  nose  or  pharynx,  or  mild  attacks 
of  the  disease  wliich  have  not  been  recogni/Anl, 
may  cause  the  development  of  antitoxin.  As  stat- 
ed in  an  earlier  chapter,  the  loss  of  suitable  re- 
ceptors may  be  a  factor  in  this  type  of  acquired 
immunity. 

Hypertrophic  tonsils  and  chronic  pharyngitis 
appear  to  be  predisposing  causes  in  children. 
Active  Spontaneous  recovery  (active  immunity)  is  due 
solely  to  the  formation  of  the  specific  antitoxin 
by  the  tissues  of  the  patient.  We  may  regard  the 
relationship  of  the  leucocytes  to  diphtheritic  in- 
fection as  not  definitely  settled.  Although  leuco- 
cytosis  is  a  fairly  constant  occurrence  and  may  go 
as  high  as  25,000  to  30,000  to  the  cubic  milli- 
meter, it  is  difficult  to  dissociate  that  due  to  the 
diphtheritic  infection  from  that  caused  by  a  mixed 
infection  with  the  streptococcus.  Both  polynu- 
clears  and  mononuclears  are  increased,  the  latter 
being  especially  marked  in  children  (Ewing). 
That  the  polymorphonuclear  leucocytes  may  ingest 
diphtheria  bacilli  was  shown  by  Wright  and  Doug- 
lass, the  influence  of  opsonins  being  essential  for 
phagocytosis.  Certain  observers  hold  that  a 
marked  leucocytosis  is  an  unfavorable  prognostic 
sign,  although  Besredka  and  others  take  the  oppo- 
site view. 

The  duration  of  active  immunity  to  diphtheria 
varies  greatly.  Usually  an  individual  has  diph- 
theria but  once,  yet  not  infrequently  those  are  en- 
countered who  suffer  from  repeated  attacks.  In 
some  instances  the  susceptibility  continues  into 
adult  life. 
Prophylaxis.  The  advcut  of  serum  therapy  justifies  no  relaxa- 
tion in  the  customary  prophylactic  measures,  such 


DII'IITIIERIA.  241 

as  isolation  of  the  diseased,  quarantine  and  disin- 
fection. A  patient  should  not  be  considered  harm- 
less until  his  mouth,  pharynx  and  nose  are  free 
from  bacilli,  a  condition  which  may  be  brought 
about  by  antiseptic  applications,  and  for  the  de- 
termination of  which  repeated  bacteriologic  exam- 
inations are  necessary.  The  danger  that  others 
who  have  been  in  contact  with  the  patient  may 
carry  the  infection  should  be  met  by  appropriate 
treatment.  It  is  not  to  be  forgotten  that  anti- 
toxin does  not  destroy  the  organisms.  The  injec- 
tion of  antitoxin  is  pur  most  effective  measure  for 
individual  prophylaxis. 

The  efficacy  of  diphtheria  antitoxin  is  so  well  Serum 
known   that    little   comment   is    needed.      It    has      ^"'•y- 
caused  a  reduction  of  more  than  50  per  cent,  in 
the  mortality  of  the  disease;  from  41  per  cent,  to 
8  or  9  per  cent.,  according  to  Baginsky. 

For  prophylaxis  from  500  to  1,000  units  are 
generally  recommended,  although  some  foreign 
authorities  give  only  250  units.  Earely,  individ- 
uals who  have  received  such  treatment  develop 
diphtheria  within  twenty-four  hours  after  the  in- 
jection. In  these  cases  it  is  probable  that  infec- 
tion has  already  occurred  and  symptoms  appear 
before  the  antitoxin  is  thoroug|J.ily  distributed. 
Naturally  one  may  contract  diphtheria  after  the 
antitoxin  is  eliminated. 

For  curative  purposes  the  amount  actually  re- 
quired depends  on  the  virulence  of  the  infection  . 
and  the  duration  of  the  disease.  Inasmuch  as  the 
virulence  may  not  be  known  accurately,  what  ap- 
pears to  be  an  excess  of  antitoxin  is  always  de- 
manded. Having  in  mind  the  average  dose  of 
3,000  units  recommended  by  the  recent  edition  of 


242  IXFECTIOy  AND  IMMUXITY. 

the  United  States  Phaniuu-opeia,  the  pliysician 
must  be  guided  by  the  eonditions  in  the  individ- 
ual ease.  Less  than  2,000  units  are  rarely  indi- 
cated, and  as  many  as  10,000  and  14,000  units 
may  be  given  -without  detriment  to  the  patient. 
There  should  be  no  hesitation  about  repeating  a 
dose  within  twenty-four  hours  in  the  absence  of 
distinct  improvement. 

Eansom  and  Knorr  state  that  if  the  antitoxin 
is  given  intravenously,  which  may  be  done  without 
danger,  the  action  of  the  serum  is  about  eight 
hours  earlier  than  when  given  subcutaneously.  In 
severe  and  in  late  cases  it  is  advisable  to  use  this 
method  of  introduction,  the  serum  first  being 
warmed  to  the  temperature  of  the  body. 

It  is  probable  that  few  cases  are  so  mild  or  so 
hopeless,  unless  moribund,  tliat  the  omission  of 
antitoxin  is  justifiable. 
Diphtheritic  The  belief  that  antitoxin  favors  the  development 
of  diphtheritic  paralysis  is  no  longer  held.  If 
there  has  been  an  actual  increase  in  the  percentage 
of  cases  which  suffer  from  paralysis,  as  sometimes 
stated,  it  is  because-  a  larger  number  of  severe 
cases  is  saved ;  and  the  severe  cases  are  those  which 
most  frequently  develop  paralysis.  If  we  accept 
the  view  of  Ehrlich  that  a  special  toxin  of  weak 
affinity  for  the  antitoxin,  i.  e.,  the  toxon,  causes 
the  paralysis,  we  find  all  the  more  justification 
for  large  doses  of  antitoxin,  for  antitoxin  neutral- 
izes the  toxon  as  well  as  the  toxin.  On  the  basis 
of  experimental  work  Eansom  concludes :  "Trans- 
ferring the  results  (of  experiments)  to  practice 
among  human  beings,  we  may  expect  liberal  doses 
of  antitoxin  given  early  in  the  illness  to  influence 
favorably  the  subsequent  paralysis;  and   this  fa- 


Paralysis. 


niPJITHERIA.  243 

vorable  influence  is  likely  to  manifest  itself,  not  so 
much  in  the  local  paralyses  (soft  palate,  etc.),  as 
in  such  fatal  symptoms  as  failure  of  the  heart. 
Severe  cases,  however,  are  likely  to  be  followed  by 
some  paralysis  in  spite  of  even  large  closes  of  anti- 
toxin/' 

Cases  in  which  there  is  severe  mixed  infection, 
septic  diphtheria,  respond  less  favorably  to  anti- 
toxic therapy  than  vmcomplicated  cases.  At  some 
time  a  mixed  serum  therapy  suited  to  the  mixed 
infection  may  be  possible. 

The  siiggestion  made  by  Wasserman  of  a  com- 
bined treatment  with  bactericidal  and  antitoxic 
serums  has  not  been  applied  practically. 

Inasmuch  as  the  serum  of  the  patient  does  not  Agglutination 
develop  agglutinins,  the  agglutination  test  is  of  ^*'' 
no  value  for  the  recognition  of  the  disease.  If  ani- 
mals are  immunized  with  the  bacillus,  agglutinins 
are  said  to  be  formed.  The  serum  of  such  an  ani- 
mal may  be  used  for  the  identification  of  a  culture 
made  from  the  throat,  but  this  would  have  no 
practical  value,  for  the  diagnosis  may  be  estab- 
lished by  the  ordinary  bacteriologic  methods  much 
more  quickly  and  satisfactorily.  It  is  difficult  to 
obtain  a  homogeneous  suspension  of  the  bacillus 
for  the  agglutination  test.     > 

Microscopically  and  culturally  the  bacillus  of  Pseudodiph 
diphtheria    can   be    distinguished    with    difficulty  th^^a  B««:'"'i- 
from  a  variety  of  other  organisms  which  belong  to 
the  same  group,  and  which  are  called  pseudodiph-    - 
theria  bacilli.     The  latter  are  frequently  found  in 
diphtheritic  throats,  but  occur  also  in  the  upper 
air  passages  and  conjunctiva  in  the  absence  of  all 
lesions.     On  the  whole,  they  are  non-pathogenic, 
but  occasionallv  a  culture  is  found  which  causes  a 


24-4  lyFECTIOX  AM)  IMMUMTY. 

subcutaneous  infiltration  at  the  point  of  injection 
in  an  experimental  animal.  Hamilton  cultivated 
one  which  Avas  distinctly  virulent  for  animals.  Their 
pathogenicity,  however,  is  altogether  different 
from  that  of  the  diphtheria  bacillus  inasmuch  as 
diphtheria  antitoxin  does  not  protect  against  them 
nor  do  animals  which  are  immunized  with  pseudo- 
diphtheria  bacilli  become  immune  to  the  toxin  of 
diphtheria.  The  Bacillus  xerosis,  which  is  thought 
by  some  to  be  the  cause  of  xerosis  conjunctivae, 
but  which  is  also  found  under  normal  conditions, 
is  a  pseudodiphtheria  bacillus.  The  animal  experi- 
ment is  the  only  positive  means  of  differentiating 
the  true  from  the  pseudodiphtheria  bacilli.  Some 
consider  them  as  diphtheria  bacilli  which  have  lost 
their  virulence. 

The  presence  of  these  organisms  may  complicate 
the  diagnosis  of  diphtheria  in  some  cases,  but 
there  is  little  danger  of  serious  error.  If  one 
found  organisms  resembling  the  bacillus  of  diph- 
theria in  a  membranous  sore  throat  which  was  ac- 
companied by  severe  s}miptoms,  there  could  be  no 
wavering  in  the  decision  to  use  antitoxin. 

II.    TETANUS. 

In  1884  Carle  and  Eattone  demonstrated  the 
infectiousness  of  tetanus  by  inoculating  the  pus 
from  an  infected  wound  into  rabbits;  11  of  the  12 
inoculated  rabbits  died  of  tetanus.  In  1885  the 
bacillus  was  discovered  by  Nicolaier,  and  Kitasato 
cultivated  it  artificially  in  1889. 
Characteristics  The  Organism  is  rather  long  and  slender  (2  to 
4  microns  long,  0.3  to  0.5  broad),  possesses  many 
ilagella  and  has  a  small  amount  of  motility.  It 
stains  readily  with  the  ordinary  anilin  dyes  and  by 


of  the  Micro- 
orflanism. 


TETANUi^.  245 

Gram's  method.  In  young  cultures  isolated  cells 
and  threads  predominate,  but  after  a  few  days 
spore  formation  begins;  eventually  all  the  adult 
cells  degenerate  and  the  culture  consists  entirely 
of  spores.  The  spores  have  a  larger  diameter  than 
the  bacillus;  are  situated  at  one  end  of  the  cell  and 
give  the  latter  the  characteristic  "drumstick" 
form.  The  organism  is  a  strict  anaerobe  and  is 
obtained  in  pure  culture  with  some  difficulty. 
Morphologically  it  is  difficult  to  distinguish  from 
the  bacilli  of  malignant  edema  and  symptomatic 
anthrax. 

Few  organisms  are  distributed  more  widely  and  Habitat. 
generously  than  the  bacillus  of  tetanus.  It  is  most 
abundant  in  street  dirt  and  in  tilled  ground  which 
has  been  fertilized  with  manure.  Nicolaier  found 
it  in  twelve  out  of  eighteen  samples  of  earth.  It 
is  less  abundant  in  timber  land.  Such  a  distribu- 
tion is  easily  accounted  for,  since  the  bacillus 
seems  normally  to  be  an  inhabitant  of  the  intesti- 
nal tract  of  the  horse,  cow  and  sheep,  and  is  often 
found  in  that  of  man  and  other  animals.  It  oc- 
curs on  dirty  clothing  and  readily  gains  access  to 
dwellings  with  dust  in  which  it  may  be  blown  and 
carried  about.  Tetanus  frequently  develops  in 
gunshot  wounds  in  which  dirty  clothing  is  carried 
into  the  tissue,  and  several  instances  of  house 
tetanus  have  been  noted  in  which  a  number  of  in- 
dividuals in  the  same  dwelling  have  contracted  the 
disease  following  injury.  Particular  localities  may 
be  heavily  infected.  In  certain  tropical  districts  a 
large  percentage  of  the  new  born  die  of  tetanus 
neonatorum,  and  puerperal  tetanus  has  prevailed 
alarmingly  in  Bombay.  It  has  been  suggested 
that  the  custom   of  bleaching  the  linen   on  the 


246  INFECTION  AND  IMMUNITY. 

ground  may  be  responsible  for  the  prevalence  of 
tlie  disease  in  these  localities,  but  from  the  fact 
that  it  has  decreased  under  aseptic  practices  the 
general  lack  of  surgical  precautions  is  probably  of 
greater  importance.  Tetanus  has  resulted  from 
the  injection  of  impure  gelatin  for  hemostatic 
purposes.  The  bacillus  has  been  found  in  sea 
water. 

The  ability  of  the  bacillus  to  proliferate  outside 
the  animal  body  has  not  been  determined.  Some 
observers  liold  that  it  exists  as  a  vegetative  organ- 
ism only  in  the  intestinal  tract  of  animals,  but  the 
possibility  of  proliferation  in  soil  is  by  no  means 
excluded,  particularly  since  it  is  so  often  found  in 
association  with  organisms  which  are  known  to 
favor  its  growth.  When  incrusted  in  solid  ma- 
terial and  accompanied  by  suitable  saprophytes  it 
may  readily  find  the  anaerobic  conditions  which 
are  demanded  for  germination  of  the  spores. 
Resistance.  The  sporcs  are  very  resistant.  In  one  instance 
they  remained  virulent  for  eleven  years  "on  a  splin- 
ter of  wood.  They  may  be  killed  in  six  days  by 
direct  sunlight.  In  comparison  with  non-spore- 
forming  organisms  they  are  very  resistant  to  anti- 
septics. Kitasato  found  that  they  were  killed  in 
five  minutes  by  steam,  in  fifteen  hours  by  a  5  per 
cent,  carbolic  acid,  in  two  hours  by  5  per  cent, 
carbolic  acid  to  which  0.5  per  cent,  of  hydro- 
chloric acid  was  added,  in  three  hours  by  1/1000 
corrosive  sublimate  and  in  thirty  minutes  by  the 
same  solution  to  which  0.5  per  cent,  hydrochloric 
acid  had  been  added. 

Tetanus  is  conspicuously  a  wound  infection  and 
that  it  develops  so  frequently  from  wounds  which 
are  contaminated  with  earth  is  readilv  understood 


TETANUS.  247 

from  the  distribution  of  the  organisms  as  cited  infection  Atria 

,  /^         •  T      ■  1  ii'j  1  i>    and  Conditions 

above.  Considering,  however,  the  great  number  ol  which  Favor 
such  wounds  and  the  prevalence  of  the  bacillus,  "  *«^t">"- 
the  rarity  of  the  disease  is  remarkable.  In  expla- 
nation of  this  fact  investigations  have  shown  that 
the  organism  is  not  a  vigorous  parasite,  that  it 
demands  special  conditions  for  its  development  in 
the  tissues.  According  to  Vaillard  and  Rouget, 
the  spores  when  washed  free  of  toxin  do  not  cause 
tetanus,  but  rather  are  taken  up  and  destroyed  by 
leucocytes. 

The  bacillus,  furthermore,  is  a  strict  anaerobe,  Anaerobic 
demanding  for  its  development  a  wound  from  li^wounds. 
which  the  air  is  largely  excluded.  It  is  well  known 
that  penetrating  wounds  in  which  infected  ma- 
terial is  carried  beneath  the  fasciae,  as  the  rusty 
nail  wounds,  also  those  accompanied  by  deep  lac- 
erations, as  wounds  inflicted  with  blank  cartridges, 
or  those  in  which  dirt  and  micro-organisms  have 
been  ground  into  the  tissues,  as  in  crushing  inju- 
ries, are  prone  to  be  followed  by  tetanus.  Under 
such  conditions  the  bacillus  lies  deeply  imbedded 
in  the  tissues  and  remote  from  the  air. 

Of  equal  importance  is  the  presence  of  foreign  mhibitionof 
matter  and  particularly  of  other  micro-organisms,  •'•'agocytosis. 
Relatively  superficial  wounds  in  which  there  is 
laceration  of  the  tissue  with  consequent  necrosis, 
as  in  wounds  by  toy  pistols,  even  the  paper-cap 
pistol,  are  well  adapted  for  the  development  of 
tetanus  if  the  germs  were  on  the  skin  at  the  time 
of  injury.  Kecrotic  tissue  favors  the  proliferation 
of  the  tetanus  bacilli  in  two  ways.  In  the  first 
place  it  seals  up  the  wound  to  a  certain  extent, 
and  thus  provides  the  requisite  anaerobic  condi- 
tion ;  in  the  second  place  it  would  seem  to  prevent 


Infections, 


248  IXFECTION  AND  IMMUNITY. 

phagocytosis  of  the  bacilli  in  some  obscure  way. 
It  has  been  suggested  that  the  strong,  cheraotactic 
relation  which  exists  between  necrotic  material 
and  leucocytes  causes  the  latter  to  take  up  the  dead 
tissue  rather  than  the  bacilli.  That  innocent  for- 
eign material  may  favor  the  development  of  teta- 
nus in  the  presence  of  the  microbes  was  shown  by 
Vaillard  and  Rouget:  tetanus  would  develop  in 
the  presence  of  an  artificially  produced  hematoma 
or  a  subcutaneous  fracture  while  in  the  absence  of 
such  predisposing  factors  the  bacilli  were  taken  up 
by  phagocytes. 
Mixed  Saproplniic  organisms  and  the  pus-producing 
cocci  which  are  usually  found  in  wounds  contami- 
nated with  earth  appear  to  favor  the  development 
of  tetanus.  This  may  be  explained  to  some  extent 
by  their  ability  to  increase  the  virulence  of  the 
tetanus  bacillus,  a  condition  which  is  noted  in  cul- 
tures. In  the  wound  they  may  engage  the  leuco- 
cvtes  in  phagocytosis  and  prevent  ingestion  of  the 
tetanus  l3acilli.  As  aerobic  organisms  they  may 
facilitate  development  of  the  bacilli  by  consuming 
local  oxygen. 

Our  great  harvest  of  tetanus  following  Fourth 
of  July  injuries  is  closely  associated  in  the  first 
place  with  the  warm,  dry  season  in  which  the 
bacilli  are  more  readily  disseminated  with  dust, 
and  in  the  second  place  with  the  nature  of  the 
wound  and  mixed  infections,  as  described  above. 

Occasionally  tetanus  follows  the  simplest 
wounds,  which  may  have  healed  entirely  before 
symptoms  develop.  In  "idiopathic  tetanus"  and 
in  the  so-called  "tetanus  rheumaticus,"  which  fol- 
lows exposure  to  cold,  the  infection  atria  are  un- 
known.    In  the  latter  instance  a  latent  infection, 


TETANUS.  249 

which  is  stirred  into  activity  by  the  reduction  of 
resistance  which  often  follows  exposure^,  may  be 
present;  avirulent  tetanus  bacilli  (?)  were  culti- 
vated from  the  lungs  of  one  such  patient.  The  oc- 
casional occurrence  of  tetanus  following  diphthe- 
ria and  typhoid  suggests  that  infection  may  take 
place  through  wounds  of  mucous  surfaces.  Neither 
the  bacillus  nor  its  toxins  penetrate  the  unbroken 
skin  or  mucous  membranes,  and  the  alimentary 
tract  is  further  protected  by  the  ability  of  the  gas- 
tric and  pancreatic  juices  to  digest  the  toxin. 

The  incubation  period  varies  from  two  or  three  Period  of 
days  to  several  weeks.    In  the  statistics  of  Eose  20    "*^"  ^*'**"' 
per  cent,  of  the  cases  showed  symptoms  in  the  first 
week,  45  per  cent,  in  the  second,  and  about  30  per 
cent,  in  the  third  or  fourth  weeks.     The  shorter 
the  incubation  period  the  more  fatal  the  disease. 
In  the  statistics  cited  the  mortality  with  short  in- 
cubation was  91  per  cent.;  when  the  incubation  ■ 
period  was  moderate  it  was  81.3  per  cent.,  and 
when  prolonged,  52.9  per  cent.     The  nearer  the 
infection  atrium  is  to  the  central  nervous  system 
the  shorter  is  the  incubation  period;  'Tiead  teta- 
nus" develops  quickly. 

The  pathogenic  properties  of  the  tetanus  bacil-  Pathogenesis. 
lus  reside  in  its  soluble  toxins,  of  which  two,  teta- 
nospasmin  and  tetanolysin,  are  loiown.  The  char- 
acteristic nervous  phenomena  of  the  infection  de- 
pend on  the  action  of  the  former,  whereas  the  lat- 
ter, a  hemolytic  toxin,  is  of  minor  importance.  As 
in  diphtheria,  a  systemic  distribution  of  the  bacilli 
is  not  necessary  for  the  development  of  the  dis- 
ease, the  toxin  being  produced  by  the  organisms  in 
the  woimd,  whence  it  is  carried  to  the  nervous 
tissue  by  way  of  the  lymphatics.     Particularly  in 


250  INFECTION  AND  IMMUNITY. 

.  mixed  infections  tetanus  bacilli  may  be  carried  to 
neighboring  lymphatic  glands  and  eventually 
reach  the  circulation;  pure  cultures  have  been  ob- 
tained from  the  lieart's  blood  in  experimental 
work.  The  blood,  on  account  of  its  content  in 
oxygen,  is  thought  to  be  unfavorable  for  the 
growth  of  the  organism. 

Just  before  death  the  toxin  has  been  demon- 
strated in  the  blood  of  man  by  injecting  some  of 
the  serum  into  mice.  Its  excretion  in  the  urine  is 
questionable.  Tetanus  produces  no  characteristic 
anatomic  changes,  although  degenerative  lesions 
in  the  ganglionic  cells  occur.  Death  usually  occurs 
from  asphyxia  caused  b)''  contractions  of  the  dia- 
phragm, or  muscles  of  the  glottis,  or  from  cardiac 
failure.  In  some  instances  the  blood  has  been 
found  more  or  less  laked  because  of  the  action  of 
the  tetanolysin. 
Tetanospasmin.  Tetanus  toxin  (tetanospasmin)  has  a  very 
strong  affinity  for  the  nervous  tissue  of  susceptible 
animals.  This  may  be  demonstrated  in  test-tube 
experiments  in  which  the  toxin  is  mixed  with  an 
emulsion  of  the  nervous  tissue;  the  nervous  tissue 
neutralizes  the  toxin  more  or  less  completely,  as 
determined  by  subsequent  inoculations  of  the  mix- 
ture (Wasserman's  experiment).  It  is  held  by 
certain  authorities  that  the  toxin  attacks  only  the 
nervous  tissue  in  man;  in  some  of  the  lower  ani- 
mals, however,  various  organs,  especially  the  liver, 
have  an  affinity  for  the  toxin. 

The  method  by  which  tetanus  toxin  reaches  the 
central  nervous  system  has  been  the  subject  of 
much  speculation  and  experimentation.  Eecent 
observations  by  jMarie  and  ]\Iorax  and  by  Eansom 
and  Meyer  show  with  a  great  degree  of  probabil- 


.      TETANUS.  251 

ity  that  it  is  absorbed  by  the  end  organs  of  the 
motor  nerves  and  from  there  passes  to  the  gang- 
lionic cells  through  the  axis  cylinders.  This  ab- 
sorption takes  place  very  quickly;  when  the  toxin 
is  given  intravenously  it  disappears  from  the  blood 
in  the  course  of  minutes.  It  has  been  found  in  the 
nerves  within  an  hour  and  a  half  after  subcutane- 
ous injection.  Its  further  transmission  centrally 
occupies  more  time  and,  indeed,  the  investigators 
mentioned  explain  the  rather  long  incubation 
period  of  the  disease  on  the  basis  of  the  time  re- 
quired for  this  transmission.  The  brief  incuba- 
tion period  in  "head  tetanus,"  accordingly,  would 
depend  on  the  short  distance  the  toxin  is  obliged 
to  travel  to  reach  the  ganglionic  cells. 

Although  the  toxin  appears  not  to  be  taken  up  varieties  of 
by  the  sensory  nerves,  a  painful  form  of  the  dis-  Tetanus. 
ease,  tetanus  dolorosa  (Meyer),  may  be  pro- 
duced experimentally  by  injecting  the  toxin  into 
the  posterior  roots  of  the  spinal  nerves.  Eoux 
caused  "cerebral  tetanus"  by  introducing  the  toxin 
into  the  cerebral  tissue;  the  condition  is  charac- 
terized by  absence  of  contractures.  "Local  teta- 
nus," in  which  the  muscles  in  the  vicinity  of  infec- 
tion or  inoculation  are  involved  in  contractures,  is 
the  first  symptom  of  tetanus  in  experiment  ani- 
mals; it  rarely  occurs  in  man  except  in  head  teta- 
nus. The  phenomenon  depends  on  the  fact  that 
the  toxin,  being  transmitted  through  the  motor 
nerves,  reaches  first  the  ganglionic  cells  which  cor- 
respond to  the  infected  area. 

According  to  ]\Ietchnikoif,  the  only  natural  im-  immunity 
munity  which  man  possesses  to  tetanus  is  leuco-  '"   *"' 
cytic  and  this  may  be  sufficient  to  protect  under 
favorable  conditions.  The  observations  of  Vaillard 


252  IXFECTION  AXD  IMMUXITY. 

and  Eoiiget  (cited  above)  support  this  claim.  Sus- 
ceptibility depends  not  onlj-  on  the  presence  of 
suitable  receptors  in  the  nervous  tissue,  but  also 
on  the  degree  of  affinity  which  exists  between 
tliese  receptors  and  the  toxin.  In  man  and  some 
animals  this  affinity  is  very  great,  whereas  in  fowls 
it  is  weak  and  an  enormous  amount  of  toxin  is  re- 
quired to  cause  tetanus.  A  further  proof  of  this 
weak  affinity  in  non-susceptible  animals  rests  in 
the  fact  that  the  toxin  when  injected  into  the  blood 
remains  unabsorbed  for  a  long  time,  whereas  in 
susceptible  animals  it  disappears  very  quickly.  Ac- 
quired immunity  depends  on  the  presence  of  anti- 
toxin in  the  circulation. 
Prophylactic  Tctanus  antitoxin  is  a  thorough  prophylactic. 
Antitoxin.  This  fact  has  been  heralded  so  extensively  in  re- 
cent years  that  there  can  be  little  excuse  for  ignor- 
ance on  the  part  of  any  physician.  At  the  same 
time,  the  returns  from  the  "Fourth"  show  that  the 
principle  is  not  yet  deeply  imbedded  in  the  medical 
mind.  It  is  quite  certain  that  a  large  percentage 
of  these  fatalities  could  be  prevented  by  two  injec- 
tions of  antitetanic  serum,  one  at  the  time  of  in- 
jury and  a  second  from  five  to  eight  days  later. 
An  epidemic  of  puerperal  tetanus  in  an  obstetric 
ward  in  Prague  was  checked  by  prophylactic  injec- 
tions of  the  antitoxin.  In  a  certain  section  of 
France  4,000  horses,  with  injuries  commonly  fol- 
lowed by  tetanus,  received  antitoxin  and  none  de- 
veloped the  disease. 

No  degree  of  efficacy  on  the  part  of  the  anti- 
toxin, however,  justifies  disregard  of  the  surgical 
care  which  the  wound  demands.  From  the  facts 
cited  it  is  clear  that  thorough  and  frequent  disin- 
fection of  the  wound,  free  drainage,  the  removal 


TETANUS.  253 

of  all  foreign  and  necrotic  material,  and  the  ac- 
cess of  air  are  measures  of  eminent  importance. 
Punctured  wounds  should  be  opened  up.  Anti- 
toxin, preferably  as  a  powder,  may  be  used  in  the 
wound,  and  the  serum  infiltrated  into  the  adjacent 
tissue. 

The  principles  which  apparently  underly  the  ill  curative  Vaiue 
success  of  the  antitoxin  as  a  curative  agent  were  **  Anntoxm. 
treated  of  in  Chapter  XVI,  Part  I.  Its  adminis- 
tration as  early  as  possible  after  symptoms  have 
appeared  is  demanded.  After  symptoms  have  ex- 
isted for  more  than  thirty  hours  Behring  main- 
tains that  there  is  no  hope  of  cure  by  the  subcuta- 
neous route.  Inasmuch  as  forty  hours  or  more  are 
required  for  complete  absorption  from  the  subcuta- 
neous tissue,  intravascular  injection  of  at  least  the 
first  dose  would  seem  to  be  indicated.  Yet  by 
neither  of  these  methods  is  the  most  essential  end 
accomplished,  for  the  antitoxin  does  not  reach  the 
nerves  nor  can  it  be  recognized  in  the  cerebrospinal 
fluid  in  conspicuous  quantities.  The  most  that 
such  injections  accomplish  is  the  neutralization  of 
the  circulating  toxin,  that  which  is  not  yet  on  its 
way  to  the  central  nervous  system  through  the  mo- 
tor nerves.  It  is,  of  course,  important  to  neutral- 
ize the  circulating  toxin  and  it  must  be  done  quick- 
ly, for  in  the  course  of  a  few  hours  the  fatal  quan- 
tity of  toxin  may  have  been  absorbed;  "a  dose  of 
antitoxin  which  would  save  in  the  morning  may 
be  without  effect  in  the  evening." 

At  the  same  time  it  is  of  greater  immediate  im-  Method  of 
portance  to  neutralize  that  which  has  already  en-  Antitoxin. 
tared  the  peripheral  nerves,  and  if  possible  to  tear 
away  some  of  the  toxin  already  bound  by  the  gang- 
lionic cells.     To  accomplish  this  object,  or  to  at- 


254  IXFI-JCTJOy  AXD  IMML MTV. 

tempt  it,  special  procedures  are  demanded.  "We 
may  then  consider  the  antitoxic  treatment  as  fol- 
lows : 

First:  The  neutralization  oL"  the  toxin  which 
has  already  been  absorbed  by  the  peripheral  nerves 
and  spinal  cord  at  a  point  as  near  the  vital  centers 
as  possible.  This  involves  surgical  exposure  of  the 
large  nerves  of  the  part  as  near  the  trunk  as  possi- 
ble and  their  infiltration  with  antitoxin  (Ransom 
and  Meyer),  and  in  desperate  cases  the  infiltra- 
tion of  the  antitoxin  in  the  spinal  cord  in  the 
vicinity  of  the  medullary  centers.  From  five  to 
fifteen  minims  may  be  injected  into  the  nerve 
trunks  at  a  sitting,  and  the  operation  may  be  re- 
peated on  subsequent  days;  the  needle  should  be 
partially  withdrawn  and  reinserted  in  different  di- 
rections during  the  injection.  Eogers  recommends 
tying  loose  ligatures  around  the  nerves  after  the 
operation  so  that  they  may  be  readily  drawn  up 
and  identified  for  further  injections.  In  order  to 
reach  the  medulla  the  intracerebral  method  of 
Roux  or  that  of  Rogers  may  be  utilized.  Kocher 
has  devised  a  technic  for  the  intracerebral  injec- 
tions. Anterior  to  the  parieto-frontal  suture  and 
to  one  side  of  the  median  line  the  scalp  is  pre- 
pared, and  a  hole  drilled  through  the  skin  and 
skull,  having  its  direction  toward  the  foramen 
magnum.  By  means  of  a  long  needle,  the  ventri- 
cle is  penetrated  and  the  serum,  after  injection, 
finds  its  way  to  the  fourth  ventricle  to  the  imper- 
iled respiratory  and  cardiac  centers;  10  c.c.  may 
be  injected.  Rogers  seeks  to  accomplish  the  same 
end  by  a  different  technic.  He  introduces  the 
needle  between  the  sixth  and  seventh  cervical  ver- 
tebrae, punctures  the  cord  deeply,  and  injects  from 


TJ^TANUH.  255 

20  to  30  minims  at  a  sitting.  Although  there  is 
danger  of  intraspinal  hemorrhage  in  the  proce- 
dure, no  ill  effects  were  noted.  It  has  been  recom- 
mended also  that  the  cerebrospinal  fluid  be  with- 
drawn by  means  of  lumbar  puncture  and  substi- 
tuted by  antitoxin.  Some  physicians  who  have 
"iised  this  method  report  favorable  results. 

Second :  The  neutralization  of  all  toxin  which, 
is  not  yet  bound  by  the  nervous  tissue  or  absorl)ed 
by  the  motor  nerves.  This  demands  the  infiltra- 
tion of  the  wound  and  surrounding  tissue  with  the 
antitoxin,  and  injection  of  a  sufficient  amount  of 
the  serum  into  the  circulation  in  order  that  circu- 
lating toxin  may  be  neutralized.  The  intraneural, 
intraspinal  or  intracerebral  injections  should .  al- 
ways be  supplemented  by  subcutaneous  or  intra- 
vascular injections.  The  first  dose  should  be  given 
intravenously,  whereas  subsequent  injections  may 
be  given  subcutaneously.  The  injections  should 
always  be  repeated. 

Unfortunately,  tetanus  antitoxin  is  not  stand-  standardiza- 
ardized  by  American  manufacturers  and  dosage  toxin! 
can  not  be  controlled  with  any  accuracy.  Although 
standardization  can  not  be  accomplished  with  the 
same  degree  of  accuracy  as  in  the  case  of  diphthe- 
ria antitoxin,  its  approximate  value  can  be  deter- 
mined (within  5  or  6  per  cent.),  which  is  suffi- 
cient for  practical  purposes.  The  antitetanic 
serums  of  Behring,  Tizzoni  and  the  Pasteur  Insti- 
tute are  all  standardized,  but  on  somewhat  differ- 
ent bases.  Behring  advises  the  administration  of 
20  units  of  his  serum  for  prophylactic  purposes, 
and  100  units  as  the  "simple"  curative  dose  when 
given  soon  after  the  development  of  symptoms. 

N'ot  less  than  10  c.c.  of  American  serum  should 


Bacillus 
Botulinus. 


Infected 
Meats. 


250  IXFKCTWX  AXD  IMMUXITY. 

be  givcu  for  prophylaxis,  and  the  dose  should  be 
repeated.  No  definite  limits  can  be  given  as  to  the 
amount  which  may  reasonably  be  given  for  cura- 
tive purposes.  Ten  cubic  centimeters  given  intra- 
venously at  once,  and  an  equal  amount  subcutane- 
ously  on  subsequent  days,  would  seem  to  be  suffi- 
cient to  neutralize  the  unbound  toxin  if  the  serum' 
has  reasonable  strength.  Standardized  serums  cer- 
tainly are  to  be  preferred. 

x^gglutination  has  no  practical  significanc'e  for 
diagnostic  purposes.  An  agglutinating  poAver  has 
been  noted  in  the  serum  on  the  eighth  day.  Ag- 
glutinins may  be  produced  by  immunizing  animals 
(rabbits)  either  with  the  bacilli  or  the  toxin.  In 
the  latter  case  the  formation  of  the  agglutinin  is 
due  to  the  presence  of  agglutinogenic  receptors  in 
the  toxin  solution. 

HI.   BOTULISM. 

Botulism  is  a  peculiar  form  of  meat  poisoning 
in  which  the  nervous  system  is  involved  princi- 
pally. From  twenty-four  to  thirty-six  hours  after 
the  poisonous  meat  is  eaten  salivation,  ptosis,  dila- 
tation of  the  pupils  and  paralysis  of  the  ocular 
muscles  develop  and  death  from  bulbar  paralysis 
occurs  rapidly  in  from  25  to  30  per  cent,  of  the 
cases.  In  the  event  of  recovery,  convalescence  may 
extend  over  weeks  or  months. 

The  disease  occurs  especially  in  some  European 
districts  in  which  improperly  preserved  or  raw 
meats  are  eaten.  The  term  ichthyosismus  is  ap-  . 
plied  to  a  similar  or  identical  disease  which  is 
caused  in  Russia  by  salted  fish.  In  1895  von 
Ermengem  investigated  a  ham  which  had  caused 
50  cases  of  botulism,  and  isolated  from  it  an  anae- 
robic,   spore-forming  bacillus,    which    produces    a 


BOTULISM.  257 

soluble  toxin  capable  of  causing  the  entire  symp- 
tom-complex of  the  disease.^  The  organism  pos- 
sesses flagellge,  has  limited  motility,  grows  only  in 
alkaline  media,  and  in  contrast  to  most  pathogenic 
organisms  prefers  a  relatively  low  temperature 
(18-25°  C).  It  is  probably  on  account  of  its 
physiologic  activity  at  such  temperatures  that  it 
is  able  to  produce  its  toxin  in  meats  which  have 
been  kept  in  a  cool  place.  It  is  found  in  decom- 
posed ham  and  various  sausages  (Leberwurst  and- 
Blutwurst),  and  probably  gains  access  to  the  meat 
after  the  animal  has  been  killed.  Von  Ermeji- 
gem  investigated  two  hams  from  the  same  animal. 
One  was  under  anaerobic  conditions  being  covered 
with  brine,  while  the  other  was  exposed  to  air; 
only  the  former  was  toxic.  The  organisms  may  be 
absent  from  the  superficial  portion  of  the  meat, 
but  abundant  in  the  deep  portion.  The  spores  are 
relatively  susceptible  to  heat,  being  destroyed  by 
a  temperature  of  80°  C.  for  one  hour.  Aside  from 
its  occurrence  in  meat,  nothing  is  known  of  the  li  le 
history  of  the  bacillus. 

The  disease  is  caused  by  the  toxin  which  has  al-  Toxin. 
ready  been  produced  in  the  meat  and  not  by  the 
activity  of  the  organism  after  it  has  reached  the 
alimentary  tract  (v.  Ermengem).  If  an  extract 
of  the  meat  is  made  with  water  and  the  bacteria 
removed  from  the  latter  by  filtration,  the  fluid 
shows  characteristic  toxicity  for  animals.  This 
experiment  may  be  used  for  determining  the  pres- 
ence of  botulism  toxin  in  suspected  meat.  The 
guinea-pig  is  the  most  susceptible  animal. 

1.  other  pathogenic  organisms,  especially  B.  enteritidis 
and  B.  coli  communis,  and  recently  the  paratyphoid  bacil- 
lus, have  been  found  in  poisonous  meats.  The  term 
botulism  formerly  was  applied  to  various  forms  of  meat 
poisoning. 


258  INFECTION  AND  IMMUNITY. 

According  to  v.  Ermengem,  the  bacillus  does  not 
proliferate  in  the  body,  nor  does  it  produce  toxin 
vigorously  at  body  temperature;  hence,  he  consid- 
ers it  to  be  a  strict  salprophyte — a  pathogenic  sap- 
rophyte. 

The  toxin  is  taken  up  by  the  circulation  j'roni 
the  alimentary  tract  and  is  not  destroyed  by  the 
gastric  and  pancreatic  juices,  differing  in  this  re- 
spect from  the  toxins  of  diphtheria  and  t»tanus. 
It  is  prepared  artificially  by  growing  the  organism 
anaerobically  in  suitable  bouillon  and  subsequently 
.  sterilizing  the  fluid  by  filtration.     Like  the  other 

soluble  bacterial  toxins,  it  is  susceptible  to  the  ac- 
tion of  air  and  light,  and  is  destroyed  by  n  ti'in- 
perature  of  from  60  to  70°  C. 
Pathogenesis.  That  the  toxin  has  a  special  affinity  for  the  nerv- 
ous tissues  is  evident  from  the  symptoms  of  the 
disease;  histologically,  the  ganglionic  cells  show 
degeneration  in  fatal  cases.  Further  evidence  of  a 
strong  affinity  between  the  toxin  and  nervous  tissue 
lies  in  the  ability  of  the  latter  to  neutralize  the 
toxin  in  the  test-glass.  The  toxin,  however,  ap- 
pears not  to  be  so  selective  in  its  action  on  the 
nervous  tissue  as  the  toxin  of  tetanus,  for  in  bot- 
ulism degenerations  of  the  glandular  organs,  and 
of  the  vascular  endothelium  with  consequent  hem- 
orrhages are  characteristic  anatomic  findings. 
Man  appears  to  be  very  susceptible  to  the  intoxica- 
tion, whereas  dogs,  rats,  and  cats  are  relatively  im- 
mune. The  toxin  is  pathogenic  by  suljcutaneous  or 
intravascular  injection. 

Acording  to  v.  Erfnengem,  the  bacilli  when  in- 
oculated subcutaneously  do  not  proliferate,  but  are 
taken  up  by  the  phagocytes  immediately  or  after 
thev  have  been  carried  to  other  organs.     Animals 


and  Antitoxin. 


PYOCYANJWS.  2.'5!) 

which  have  recovered  from  infection  or  which  have 
been  immunized  acquire  rather  strong  immunity 
to  subsequent  inoculations^,  the  immunity  being 
antitoxic. 

The  prophylactic  measures  consist  in  the  avoid-  Prophylaxis, 
ance  of  poorly  preserved  and  improperly  cooked 
meats,  especially  sausages.     Botulism  would  seem 
to  be  very  rare  in  this  country  where  raw  meats 
are  not  used  extensively. 

The  antitoxin  (Kempner)  has  proved  of  some 
value  in  animal  experiments,  but  its  commercial 
preparation  has  not  been  warranted  on  account  of 
the  rarity  of  the  disease. 

IV.    BACILLUS    PYOCYAlSrEUS. 

For  a  long  time  it  was  thought  that  the  "bacillus  Pathogenic 
of  blue  pus"  Avas  of  no  importance  as  an  infectious 
agent  for  man,  although  its  pathogenicity  for  ani- 
mals had  been  recognized  experimentally.  It  is 
found  with  some  frequency  in  the  blood  and  or- 
gans of  man  at  autopsy,  when  death  has  resulted 
from  some  other  infection  or  chronic  disease,  and 
in  such  instances  it  is  supposed  that  a  so-called 
"agonal  invasion"  by  the  organism  has  occurred. 
During  recent  years,  however,  several  cases  of  pri- 
mary pyocyaneus  septicemia  have  been  observed, 
the  bacillus  having  been  obtained  from  the  blood 
in  pure  cultures  during  life  or  from  the  blood  and 
organs  shortly  after  death.  It  has  been  found  as 
the  sole  organism  in  meningitis  and  vegetative  en- 
docarditis. Some  of  the  cases  indicate,  however, 
that  a  previous  lowering  of  resistance,  as  that 
caused  by  tuberculosis  and  syphilis,  is  important 
for  general  invasion  by  the  bacillus.  It  has  been 
found  several  times  in  suppurative  processes  in  the 
middle  ear,  and  would  seem  to  be  either  the  cause 


260  IXFECTION  AND  IMMUNITY. 

or  a  strong  adjuvant  in  some  cases  of  severe  enter- 
itis, especially  in  cliildern.  In  systemic  infec- 
tions, the  sjTQiptoms  are  typlioidal  in  character, 
with  high  temperature,  diarrhea  and  a  tendency 
to  the  formation  of  hemorrhages  in  the  skin  and 
internal  organs. 
Its  Manifold       The  BacUlus  pyocyaneus  is  widely  distributed 

Activities.  l  ,j      .j  j 

and  that  it  causes  sq  few  infections  is  probably  due 
to  its  low  pathogenic  power.  It  is  an  organism  of 
manifold  activities.  It  produces  a  substance,  pyo- 
cyanin,  which,  when  exposed  to  the  air,  assumes  a 
bluish  tint,  and  on  which  the  color  of  the  pus  de- 
pends; pyocyanin  is  soluble  in  chloroform.,  from 
which  it  may  be  precipitated  in  crystalline  form. 
I'nder  proper  conditions  the  organism  also  forms 

Ferments,  a  fluorcscent  pigment.  It  produces  a  strong  pep- 
tonizing ferment,  coagulates  milk,  and  in  old 
cultures  an  autolytic  ferment  is  found  which  di- 
gests many  of  the  bacilli.  As  stated  in  a  pre^^ous 
chapter,  Emmerich  and  Lowe  have  identified  a 
bacteriolytic  ferment,  pyocyanase,  which  dissolves 
the  anthrax  bacillus  and  other  organisms.  The 
ferment  natiu-e  of  this  substance  is  in  some  doubt, 
inasmuch  as  it  resists  the  boiling  temperature. 
Dietrich  thinks  its  action  is  due  to  the  production 
of  osmotic  changes.  Old  cultures  contain  a  hemo- 
lytic agent  (pyocyanolysin)  of  an  alkaline  nature, 
which  resists  boiling  and  is  not  a  true  toxin,  since 

Endotoxin,  immunization  with  it  does  not  yield  an  antitoxin 
(Jordan).  In  addition  to  the  products  mentioned, 
the  organism  secretes  a  true  soluble  toxin  for 
which.it  is  possible  to  obtain  an  antitoxin,  and 
possesses,  furthermore,  an  endotoxin  for  whicli 
an  antitoxin  can  not  be  obtained. 

The  soluble  toxin  of  Bacillus  yyacyaneus  is  not 


PYOCYANEUS.  261 

produced  in  large  amounts.  It  differs  from  the 
other  soluble  toxins  in  its  resistance  to  heat,  with- 
standing a  temperature  of  100°  C.  for  five  min- 
utes. It  produces  the  symptoms  which  are  char- 
acteristic of  infection  with  the  living  organism, 
the  principal  anatomic  changes  being  parenchyma- 
tous degenerations  and  ecchymoses,  the  latter  sup- 
posedly being  due  to  degenerative  changes  in  the 
endothelium  of  the  vessels. 

By  immunizing  with  young  cultures  grown  on  y^ntito^ic  and 
an  agar  surface  a  serum  which  is  purely  bacterid-  ggp^^s*^'**^' 
dal  is  obtained.  On  the  other  hand,  if  an  older 
toxin-containing  bouillon  culture  be  used,  the 
serum  is  both  bactericidal  and  antitoxic.  The 
serum  which  is  purely  bactericidal  has  no  power  of 
neutralizing  the  toxin.  The  toxin  solution  con- 
tains not  only  the  true  toxin,  but  also  quantities 
of  endotoxin  which  were  liberated  as  the  dead 
bacilli  were  dissolved.  Inasmuch  as  the  antitoxin 
neutralizes  only  the  true  toxin,  leaving  the  endo- 
toxin unbound,  the  toxicity  of  the  filtrate  can  not 
be  destroyed  entirely  by  antitoxin,  a  condition 
which  is  brought  out  clearly  when  the  attempt  is 
made  to  neutralize  a  multiple  of  the  simple  fatal 
dose  by  the  corresponding  amount  of  antitoxin. 
In  such  multiples  a  fatal  amount  of  endotoxin  is 
present.  Although  a  strong  antitoxin  may  be  ob- 
tained, it  would  appear  to  be  of  little  practical 
importance  because  of  the  rarity  of  infections  by 
the  bacillus. 

Infection  in  man  has  caused  the  formation  of  Agglutination. 
agglutinin  in  several  instances,   but  it  has  been 
absent  in  others.    An  agglutinating  serum  is  read- 
ily produced  by  artificial  immunization. 


The  Toxin. 


Pathogenesis. 


2G2  IXFJX'TIOy  AXD  I.UMUXITY. 

V.    OTHER   SOLUBLE  BACTERLVL   TOXINS. 

Soluble  toxins,  of  perhaps  secondary  impor- 
tance, which  are  produced  by  the  staphylococcus 
and  streptococcus,  will  be  considered  in  the  sections 
dealing  Avith  these  organisms.  It  seems  probable 
that  they  do  not  represent  tlie  essential  toxic 
agents  of  the  cocci,  but  rather  that  the  toxicity  of 
the  latter  depends  chiefly  on  the  action  of  endo- 
toxins. 

B.  INTOXICATIOX  BY  SOLUBLE  PLAXT  TOXIXS. 
I.  HAY  FEVER. 

Dunbar  separated  from  the  pollen  of  various 
grains  a  toxin  which  is  able  to  precipitate  typical 
attacks  of  hay  fever  in  those  who  are  susceptible, 
having  first  demonstrated  that  the  crude  pollens 
cause  the  disease.  The  pollen  from  the  following 
are  said  to  contain  the  toxin :  Eye,  barley,  wheat, 
maize  (corn),  dog's  tail,  couch-grass,  millet,  rice 
and  some  others.  The  so-called  autumn-catarrh 
which  is  common  in  America  may  be  due  to  a 
slightly  different  toxin  coming  from  the  golden- 
rod,  rag-weed,  and  perhaps  other  autumnal  flower- 
ing grains. 

The  toxin  usually  is  associated  with  certain 
starch-like  granules  which  are  contained  in  the 
pollen,  but  it  occurs  also  in  pollens  which  do  not 
contain  these  granules.  It  may  be  extracted  with 
water  or  salt  solution,  is  precipitated  by  alcohol, 
resists  the  boiling  temperature,  and  is  of  an  al- 
buminous nature. 

When  the  crude  pollen  reaches  the  conjunctiva, 
nasal  or  bronchial  mucous  membranes,  the  toxin 
is  dissolved  out  by  the  secretions  and  absorbed  by 
the  lymphatics.     When  applied  to  the  conjunctiva 


HAY  FEVER.  203 

it  causes  swelling,  redness  and  laclirymation.  It 
is  carried  by  the  tears  to  the  nose  and  here  causes 
excessive  secretion,  swelling  of  the  mucous  mem- 
brane and  sneezing.  It  may  become  distributed 
systemically  as  a  result  of  absorption  from  the 
free  surfaces  and  cause  the  asthmatic  attacks  and 
general  symptoms  which  are  seen  in  the  intoxica- 
tion. "When  injected  subcutaneously  into  the  arm 
both  the  asthmatic  attacks  and  coryza-like  sjmip- 
toms  were  produced. 

Dunbar's  antitoxic  serum  (poUantin)  is  ob-  Antitoxic  Serum 
tained  by  immunizing  horses  with  the  toxin.  It 
seems  to  be  of  undoubted  value  in  a  certain  per- 
centage of  cases,  but  fails  unaccountably  at  times. 
It  is,  perhaps,  most  effective  when  used  in  the 
prodromal  stage,  the  attacks  being  thereby  pre- 
vented. Its  failure  in  certain  instances  may  be 
due  in  part  to  the  inefficacy  of  the  antitoxin 
against  the  toxins  of  certain  pollens.  Again,  in 
certain  individuals  the  affinity  of  the  toxin  for 
the  tissues  may  be  unusually  great  so  that  a  more 
vigorous  use  of  the  remedy  is  demanded. 

Llibbart  and  Prausnitz  published  statistics  of 
285  cases,  of  which  65  were  autumnal.  In  ordi- 
nary hay-fever  the  serum  gave  positive  results  in 
57  per  cent.,  partially  positive  in  32  per  cent,  and 
negative  results  in  11  per  cent,  of  the  cases.  In 
autumnal  catarrh,  70  per  cent,  were  positive,  19 
per  cent,  partially  positive,  and  11  per  cent,  nega- 
tive. 

The  small  bottles  of  antitoxin  are  accompanied 
by  a  pipette  with  which  from  one  to  several  drops 
may  be  instilled  into  the  eye  or  the  nose. 


2G4  IM'IJCTION  AXD  IMMUNITY. 

The  serum  does  not  cure  permaneutly  and  one 
who  is  susceptible  should  carry  a  vial  for  imme- 
diate use  during  the  ha3'-fever  season. 

II.    OTHER  PLANT  TOXINS. 

Eicin.  from  the  seeds  of  Ricintis  coDununis; 
abrin,  from  Ahrus  precatorius;  crotin  from  the 
seeds  of  Croton  tiglium;  and  robin,  from  the  leaves 
and  bark  of  the  locust  tree  (Rohinia  pseudoacacia) 
are  chiefly  of  experimental  interest.  They  are 
similar  in  their  action,  are  very  toxic  to  animals, 
jDroducing  both  local  and  general  changes  with 
fatal  termination  when  given  in  sufficient  doses; 
they  have  pronounced  agglutinating  action  on  the 
erjiihrocj'tes  of  most  animals,  and  in  some  in- 
stances are  slightly  hemolytic.  By  guarded  im- 
munization antitoxins  may  be  obtained  for  them. 

Robert  gave  the  name  of  plialUn  to  a  toxic  sub- 
stance which  may  be  extracted  from  poisonous 
mushrooms,  particularly  the  "Deadly  Amanite" 
(Amanita  phalloides).  In  some  countries  many 
deaths  are  caused  by  eating  this  variety:  Russia, 
Germam%  Italy,  France,  Japan  (Ford).  Phallin 
is  very  toxic  for  animals  and  is  strongly  hemolytic 
for  many  bloods.  By  immunization  Ford  has  re- 
cently obtained  an  antitoxin  Avhich  neutralizes  the 
hemoMic  action  of  the  poison,  and  which  in  a  dose 
of  0.5  c.c.  protects  rabbits  against  five  fatal  doses 
of  the  toxin.  The  toxin  is  an  aqueous  extract  of 
the  dried  plants. 

C.    INTOXICATION  BY  SOLUBLE  ANIMAL  TOXINS. 
I.    POISONING  BY  SNAKE  BITES. 

The  poison  apparatus  of  snakes  consists  of  a  se- 
cretory gland  on  each  side  which  communicates 
with  a  tubular  fang  by  means  of  a  duct.     In  the 


f 


SNAKE  VENOM.  265 


passive  state  the  fangs  are  directed  backward  on  Toxic  _ 
the  roof  of  the  mouth,  but  when  the  animal  strikes 
their  points  are  made  to  project  forward  and  the 
poison  is  forced  through  the  canals  by  muscular 
compression  of  the  sac.  The  venom  is  a  glandular 
secretion. 

The  venoms  of  different  snakes  vary  a  great 
deal  in  their  toxic  properties.  The  most  impor- 
tant constituents  are  those  which  attack  the  nerv- 
ous system  (neurotoxin),  the  blood  corpuscles 
(hemolysins  and  hemagglutinins)  and  the  endo- 
thelium of  the  blood  vessels,  causing  hemorrhages 
(hemorrhagin,  an  endotheliotoxin).  The  three  are 
independent. 

The  neurotoxin  causes  death  by  paralysis  of  the 
cardiac  and  respiratory  centers.  The  hemolysin 
appears  to  be  of  less  importance  as  a  cause  of 
death. 

The  venoms  of  the  cobra,  water-moccasin,  da-  variations  in 
boia  and  some  poisonous  sea-snakes  are  essentially  tiesand'cr''" 
neurotoxic,  although  they  have  strong  dissolving 
powers  for  the  erythrocytes  of  some  animals.  In 
studying  the  hemolytic  powers  of  the  venoms  of 
cobra,  copperhead  and  rattlesnake,  Elexner  and 
Noguchi  found  cobra  venom  to  be  the  most  hemo- 
lytic and  that  of  the  rattlesnake  the  least.  They 
attribute  the  toxicity  of  rattlesnake  poison  chiefly 
to  the  action  of  hemorrhagin.  The  same  authors 
studied  the  action  of  different  venoms  on  the  cells 
of  various  animals  and  by  absorption  experiments 
found  independent  cytotoxins  for  the  testis,  liver, 
kidney  and  blood.  ISFot  only  was  there  a  distinct 
cytotoxin  for  each  organ  of  an  animal,  but  also 
for  the  same  organ  of  different  animals,  results 
which    speak    for    a    remarkable    complexity    of 


totoxins. 


% 


2GG  lyPECTIOX  AXD  IMMUXITY. 

•  venom.  Certain  venoms  contain  a  leucocytic 
toxin. 
Ferments.  That  venoms  contain  proteolytic  ferments  is 
sliown  by  their  ability  to  digest  gelatin  and  fibrin. 
This  power  may  be  related  to  the  softening  of  the 
mnseles  which  has  been  noted  clinically  in  cases  of 
poisoning.  The  rapid  decomposition  of  the  body 
wliich  follows  death  by  snake-poisoning  is  asso- 
ciated with  a  decrease  in  the  bactericidal  power  of 
the  blood,  which,  according  to  Flexner  and  No- 
guchi  depends  on  fixation  of  the  complement  by 
the  venom. 
Amboceptors       The   hcmolvsin    and   neurotoxin,    and    perhaps 

and  Comple-       ,-,  t    i       •"  ^  •   j.       e  i  j. 

ment.  otlicr  cvtolvsins  01  venom,  consist  ot  amboceptors 
which  in  themselves  are  non-toxic;  they  become 
toxic  only  through  the  aid  of  complements  which 
are  present  in  the  body  of  the  poisoned  animal. 
In  this  instance,  complement  which  usually  is  a 
source  of  protection  becomes  a  source  of  danger  to 
the  animal  possessing  it.  Not  only  does  ordinary 
serum-complement  serve  for  activation,  but  Kyes 
discovered  that  cells  (er3'throcytes)  may  contain 
another  kind  of  complement,  an  "endocomple- 
ment,"  which  activates  the  amboceptors  after  the 
latter  have  combined  with  the  cells.  Flexner  and 
ZSToguchi  found  that  this  also  was  the  case  with 
the  neurotoxic  amboceptors. 

The  ability  of  lecithin  to  activate  the  hemolytic 
amboceptors  of  cobra  venom  and  the  preparation 
of  cobra-lecithid  (Kyes)  were  described  in  Part  I, 
Chapter  XII.  pages  158-160.  In  the  preparation  of 
cobra-lecithid  the  neurotoxin  is  separated  from 
the  hemolysin,  the  former  remaining  in  solution, 
whereas  the  latter  settles  as  a  precipitate  in  com- 
bination  with  the  lecithin.     Immunization   with 


SNAKE   VENOM.  267 

the  neurotoxin  isolated  in  this  way  causes  the  for- 
mation of  a  specific  antineurotoxin  (Elliot).  The 
neurotoxin  may  also  be  abstracted  from  the  venom 
by  treating  the  latter  with  the  nervous  tissue  of  a 
susceptible  animal  (Flexner  and  Noguchi). 

The  hemolysin  is  distinct  from  the  hemagglu- 
tinin and  the  latter  may  be  eliminated  by  heating 
the  venom  to  from  75°  to  80°  C.  In  the  action  of 
venom  on  erythrocytes  agglutination  precedes  he- 
molysis. 

The  toxins  may  be  converted  into  toxoids  by   Toxoidsand 
heat  or  treatment  with  chemicals.     Immunization 
with  toxoids  causes  the  formation  of  antitoxins. 
Eadium  is  said  to  destroy  the  toxicity  of  venom 
(Physalix). 

The  antivenin  of  Calmette  is  obtained  by  im- 
munizing horses  with  a  mixture  of  venoms  (80 
per  cent,  cobra,  20  per  cent,  viperine  venom),  which 
are  attenuated  before  injection.  Six  months  are 
required  to  produce  a  strong  serum.  The  claim 
of  Calmette  that  his  serum  is  effective  against  all 
snake-venoms  is  erroneous.  It  neutralizes  those 
venoms  the  toxicity  of  which  depends  largely  on 
neurotoxins  and  hemolysins,  but  has  little  influ- 
ence on  rattlesnake  poison,  the  essential  toxin  of 
which  is  hemorrhagin.  Antivenin  for  the  rattle- 
snake and  water-moccasin  may  be  prepared  by  im- 
•munization  with  the  corresponding  venoms  which 
have  been  attenuated  by  weak  acids.  Noguchi  has 
produced  serum  of  such  strength  that  it  promises 
to  be  of  practical  value  in  the  treatment  of  rattle- 
snake bites. 

As  indicated  previously,  the  action  of  venom  is 
preceded  by  no  aj)preciable  incubation  period; 
hence,  an  antitoxin  to  be  effective  must  be  admin- 


26S  INFECTION  AND  IMMUNITl'. 

istcred  not  later  tlian  a  few  hours  after  the  bite 
has  occurred.  Noguchi  found  in  relation  to  anti- 
venin  for  the  rattlesnake  that  the  antitoxin  neces- 
sary to  save  was  quadrupled  three  hours  after  in- 
travenous injection  of  two  fatal  doses  of  venom. 
Fortunately  the  venom  is  less  toxic  when  intro- 
duced subcutaneously. 

II.    OTHER    ZOOTOXINS. 

Phrjmolysin,  which  is  present  in  the  blood  and 
skin  of  certain  toads,  has  been  studied  especially 
by  Proscher.  It  is  a  thermolabile,  hemol3rtic  toxin 
for  which  an  antitoxin  can  l)c  o1)tained  by  immuni- 
zation. 

Arachnolj'^sin,  obtained  from  the  bodies  of  cer- 
tain spiders,  is  a  hemolytic  toxin,  which  by  immun- 
ization yields  a  specific  antitoxin. 

A  poison,  with  properties  resembling  those  of 
snake  venom,  may  be  obtained  from  the  caudal 
segment  of  the  scorpion.  Antitoxin  is  produced 
by  immunization. 

Ichthyotoxin,  a  name  given  to  the  toxic  proper- 
ties of  eel  serum,  is  composed  of  a  neurotoxic  and 
a  hemotoxic  constituent. 

From  the  poisonous  glands  of  certain  fish 
{Tracliinus  draco)  a  highly  toxic,  thermolabile 
substance  is  obtainable,  for  which  an  antitoxin  can 
be  prepared  by  the  immunization  of  rabbits. 


GEOUP  II. 


Acute  infectious  diseases  caused  by  bacteria 
which  do  not  secrete  strong  soluble  toxins  in  cul- 
ture media,  but  which  contain  endotoxins  (toxic 
protoplasm).  Infection  or  immunization  causes 
immunity  of  considerable  or  prolonged  duration. 
In  active  immunity  the  serums  agglutinate  the 
corresponding  organisms  and  are  protective  for 
other  animalS;,*  but  have  little  or  no  curative 
power.  The  formation  of  antitoxins  is  not  defi- 
nitely established.  In  most  instances  vaccination 
has  been  accomplished.  Clinically  there  is  leuco- 
cytosis  in  some  instances  and  hypoleucocytosis  in 
others  (typhoid  and  Malta  fever). 
A.  The  serum  in  acquired  immunity  is  bactericidal. 

I.    TYPHOID  FEVEK. 

Eberth  first  saw  Bacillus  typhosus  in  micro- 
scopic preparations  of  the  mesenteric  lymph  gland? 
and  spleen  of  a  typhoid  corpse,  in  1880.  Koch 
also  observed  it  at  about  the  same  time,  and 
stained  it  in  the  intestinal  wall,  spleen,  liver  and 
kidney.  It  was  obtained  in  pure  culture  by  Gaffky 
in  1884. 

The  organism  is  rod-shaped,  0.5  to  0.8  by  from 
1  to  3  microns  in  dimensions,  with  nothing  char- 
acteristic in  its  morphology.  It  possesses  from  ten 
to  twelve  flagellffi  situated  at  the  end  and  on  the 
sides  and  is  actively  motile  under  suitable  condi- 
tions. It  forms  no  spores  and  is  readily  cultivated 
on  many  media. 

The  bacillus  is  one  of  the  rather  numerous  "in- 

*  This  has  not  been  established  in  regard  to  Malta  fever. 


270  JXFIJCTWX  AMP  IMMUyiTY. 

.  testinal  group"  of  organisms,  certain  members  of 
which  are  so  simihir  that  they  can  be  differentiated 
only  by  means  of  special  culture  manipulations, 
animal  experiments,  or  the  agglutinating  and  bac- 
tericidal action  of  specific  immune  serums.^ 
Distribution  of  The  Organism  has  been  cultivated  from  earth 
the  Bacillus.  ^^^  iufcctcd  Water,  and  from  the  feces,  urine, 
blood,  rose-spots  and  the  various  organs  of  typhoid 
patients.  In  many  instances  in  which  an  epidemic 
has  certainly  been  caused  by  an  infected  water  sup- 
ply attempts  to  cultivate  the  bacillus  from  the 
water  have  failed.  The  organisms  may  not  have 
been  included  in  the  samples  which  were  analyzed, 
or,  what  is  equally  probable  in  certain  instances, 
they  have  died  out  in  the  water  by  the  time  the 
disease  was  so  widespread  as  to  be  considered  epi- 
demic. Its  occurrence  in  nature  depends  on  the 
distribution  of  the  infected  excretions  of  the  dis- 
viabijity  and  oascd.  The  viability  and  virulence  of  the  bacillus 
in  water,  earth,  etc.,  vary  Avith  the  nature  of 
its  surroundings.  It  has  been  found  to  live 
for  periods  of  from  3  to  4  weeks  to  2  or  3 
months  in  water,  from  3  to  4  months  in  milk, 
from  3  to  5  months  in  surface  water,  and  from 
11  to  16  months  in  sterilized  earth;  100  days 
in  ice,  from  12  to  30  days  in  oysters,  from  50  to 
80  days  when  dried  on  clothing,  for  3  months  in 
typhoid  feces,  for  96  days  in  the  dead  body  of  an 
experiment  animal.  "When  in  water  or  moist  earth 
which  contain  many  saprophytes  its  life  is  short- 
ened.    It  survives  drying  for  many  months,  al- 

1.  Of  this  group  the  baciUus  of  dysentery,  paratyphoid 
baciUus,  BaciUus  entcriiidin  of  Giirtner,  colon  bacillus  and 
Bacilhts  alcalifjenes,  in  addition  to  the  typhoid  bacillus,  are 
the  most  important  because  of  their  similar  morphologic  and 
cultural  properties  and  the  pathogenicity  of  certain  of  them. 


TYPIIOUJ  FKVER. 


271 


Typhoid 
Epidemics. 


thougli  direct  sunligbt  kills  in  the  course  of  a  few 
hours. 

The  typhoid  bacillus  secretes  no  soluble  toxin,  Endotoxin 
but  contains  an  endotoxin  which  may  be  obtained 
in  solution  by  the  autolytic  digestion  of  cultures, 
by  extracting  ground-up  bacilli  or  by  squeezing  out 
the  plasma  under  high  pressure.  Up  to  the  pres- 
ent time,  immunization  with  none  of  these  prepa- 
rations has  resulted  in  the  production  of  an  anti- 
toxic serum  of  accepted  value. 

Typhoid  fever  may  become  epidemic  either 
through  a  contaminated  water  supply  or  by  contact 
infection.  "^^Hien  due  to  infected  water  there  is 
something  characteristic  about  the  explosive-like 
suddenness  with  Avhich  dozens  or  even  hundreds 
are  stricken  within  a  short  period.  The  water  of 
streams,  small  lakes  or  reservoirs  may  become  in- 
fected from  an  ill-constructed  out-house,  or  from 
discharges  which  have  been  thrown  on  the  ground 
in  their  vicinity.  TjqDhoid  stools  thrown  on  the 
ground  adjacent  to  wells  have  caused  miniature 
epidemics.  Fruit,  vegetables  and  milk  cans  may 
be  infected  by  washing  them  with  contaminated 
water,  and  it  is  supposed  that  the  disease  may  be 
acquired  from  oysters  Avhich  have  lain  in  water 
contaminated  with  sewage. 

By  whatever  means  an  epidemic  is  set  in  motion, 
primarily,  it  is  usually  aggravated  and  prolonged 
by  the  occurrence  of  contact  infections  (indirect 
contact).  The  hands  of  the  nurse,  physician,  or 
others  who  come  in  contact  with  the  patient  be- 
come contaminated  from  the  stools,  urine,  soiled 
linen  or  skin  of  the  patient,  and  the  organisms 
subsequently  are  transferred  to  food,  drinking 
water,  or  in  other  accidental  ways  reach  the  mouth. 


IXFECTIOX  A.yD  niMUXITY 


The  Infection 
Atrium. 


importance.  Dust 
or  feces  and  drop 
or    the    sputum    of 


Incubation 
Period 


Each  new  case  is  a  fresh  focus  from  Avhich  infec- 
tion may  be  carried  to  others,  and  the  clumces  of 
milk  and  food  infection  become  greater  as  the 
cases  multiply.  AA^ien  the  discharges  are  not  dis- 
infected or  are  improperly  disposed  of,  soil  or 
house  infection  may  occur  and  the  possibility 
of  transmission  by  germ-laden  dust  becomes  of 
infection  from  dried  iirine 
infection  from  urine,  water, 
the  patient  are  theoretical- 
1}^  possible,  but  would  seem  to  be  of  minor  sig- 
nificance. That  flies  may  carry  the  organisms 
from  open  vaults  or  cesspools  and  deposit  them  on 
food  or  in  drinking  Avater  has  been  appreciated  in 
relation  to  epidemics  in  military  camps.  Typhoid 
bacilli  have  been  cultivated  from  flies  which  were 
taken  from  the  vicinity  of  infected  material. 

The  micro-organisms  gain  access  to  the  body 
through  the  lymphoid  tissue  of  the  intestinal  tract 
(Peyer's  patches  and  the  solitary  follicles).  The 
occurrence  of  primary  infection  of  the  lungs 
through  inhalation  of  infected  dust  is  possible,  but 
has  not  been  definitely  proved.  In  this  instance 
typhoid  bacillemia  might  occur  either  with  or 
without  intestinal  infection.  In  the  latter  case  it 
would  seem  essential  that  some  local  lesion  exist 
in  the  lungs  or  elsewhere  from  which  organisms 
could  constantly  be  supplied  to  the  blood.  Neufeld 
doubts  the  ability  of  the  typhoid  bacillus  to  pro- 
liferate in  the  blood,  because  of  the  strong  bacteri- 
cidal power  of  the  latter,  and  considers  that  infec- 
tion takes  place  through  the  intestines  even  in  cases 
of  "tA-phoid  without  intestinal  lesions.'^ 

The  incubation  period  is  subject  to  considerable 
variations.     In  a  series  of  cases  in  which  the  date 


Localization 
of  the  Bacilli. 


ryPHOID  FEVER.  273 

of  exposure  was  known,  62  per  cent,  showed  symp- 
toms in  from  20  to  25  days,  2  per  cent,  in  from  14 
to  20  days,  and  3  per  cent,  later  than  30  days. 

Following  the  development  of  intestinal  lesions, 
the  bacilli  reach  the  circulation  by  way  of  the  lym- 
phatics, and  through  the  action  of  the  bactericidal 
constituents  of  the  blood  (amboceptor-complement 
complex  and  possibly  leucocytes)  they  are  killed 
and  dissolved  in  large  quantities.  It  is  now  gen- 
erally believed  that  only  through  the  disintegra- 
tion of  the  bacterial  cells  are  their  toxic  constitu- 
ents thrown  into  solution  in  the  body,  a  condition 
which  is  necessary  in  order  that  the  tissues  be  in- 
jured. Infection  of  the  blood  stream  with  living 
organisms,  in  the  early  stages  of  the  disease  and 
preceding  relapses,  occurs  in  a  large  percentage  of 
the  cases. 

It     is     possible     to     establish     the     diagnosis     of    Diagnosis  by 

typhoid  fever  by  cultivating  the  bacilli  from  the 
blood,  even  before  the  serum  has  developed  suffi- 
cient agglutinating  power  to  give  a  positive  Widal 
reaction.  A  small  flask  of  bouillon  is  inoculated 
with  from  1  to  5  c.c.  of  blood,  drawn  from  the 
median  vein  of  the  arm,  and  after  twenty-four 
hours  of  incubation  a  small  portion  of  it  is  plated 
out.  Colonies  which  devlop  on  the  plates  may  be 
identified  by  the  usual  bacteriologic  methods,  or 
the  agglutination  test  may  be  performed  with  a 
known  antityphoid  serum.  After  from  the  tenth 
to  the  fourteenth  day  the  organisms  can  rarely  be 
cultivated  from  the  blood;  the  bactericidal  sub- 
stances of  the  blood  may  have  so  increased  by  this 
time  that  circulating  bacilli  are  killed  rapidly. 

In  from  one-fourth  to  one-third  of  the  cases,  in 
the  third  week,  or  during  convalescence,  the  bacilli 


Blood  Cultures. 


274  i\fj:cti()\  1  \/>  iMMi  \rry. 

'  appear  in  large  niiinbers  in  tlie  urine,  in  \vhieh 
tliev  may  persist  for  many  weeks.  According  to 
Kanjajelf,  they  are  discharged  into  the  urine  from 
metastatic  foci  in  the  kidneys. 

Many  of  th.e  symptoms,  complications  and  se- 
quelcB  of  typhoid  fever,  as  the  rose-spots,  enlarged 
spleen,  bone  lesions,  and  in  some  instances  nervous 
lesions  and  pneumonia,  depend  on  the  distribution 
of  the  bacilli.  This  is  in  contrast  to  the  conditions 
in  diphtheria  and  tetanus,  in  which  the  distribu- 
tion of  the  bacilli  is  of  little  significance  for  the 
involvement  of  particular  organs.  The  anatomic 
changes  and  clinical  symptoms  suggest  that  the 
lymphoid  tissue  and  central  nervous  system  have 
a  special  affinity  for  the  toxic  constituents  of  the 
typhoid  bacilli. 
Endothelial  Tlic  greatest  changes  take  place  in  the  organs 
Hyperplasia,  ^lymphoid)  wliich  Contain  the  bacilli  most  con- 
stantly and  in  the  greatest  numbers.  It  is  here 
that  the  toxic  substance  may  be  j^resent  in  greatest 
concentration,  as  a  consequence  of  the  continual 
salution  of  the  organisms.  Mallory  doscrilics  an 
enormous  hyperplasia  of  the  endothelial  cells,  es- 
pecially those  of  the  lymphatic  structures.  The 
cells  are  phagocj'tic,  and  especially  in  the  lymphoid 
tissue  of  the  intestines  and  in  the  mesenteric 
lymph  glands,  englobe  and  destroy  the  lymphoid 
cells  on  a  large  scale.  It  seems  probable  that  the 
endothelial  proliferation  which  has  been  described 
is  due  to  the  rather  mild  but  prolonged  action  of 
the  dissolved  toxic  constituents  of  the  typhoid  ba- 
cillus; the  condition  is  that  of  an  inflammatory 
hyperplasia.  It  has  been  suggested  that  the  hypo- 
leu  cocytosis  of  typhoid  fever  is  due  to  the  destruc- 
tion of  the  lymphocytes  in  the  lymphoid  organs  by 
the  endothelial  phagocytes. 


TYPJIOrn  FEVER. 


275 


Mixed 
Infections. 


The  granular  and  fatty  (J cgon orations  of  the 
parenchymatous  organs  do  not  differ  from  those 
seen  in  many  acute  infections. 

The  conditions  in  the  intestinal  tract  would 
seem  to  favor  mixed  infections,  especially  hy  the 
colon  bacillus  and  streptococcus,  and  the  primary 
infection  probably  decreases  the  resistance  to  sec- 
ondary invasion.  The  role  of  the  colon  bacillus  in 
typhoid  fever  is  perhaps  not  definitely  established, 
although  it  has  been  found  in  the  circulation,  in 
abscesses,  and  in  the  urine  in  cases  of  cystitis  ac- 
companying the  disease.  The  typhoid  and  colon 
bacilli  grow  well  together.  A  mixed  general  in- 
fection with  the  streptococcus  causes  a  grave  sep- 
tic condition  characterized  by  an  irregular  tem- 
perature curve.  This  condition  may  be  discovered 
by  blood  cultures.  It  is  thought  that  the  strepto- 
coccus does  not  increase  the  toxicity  of  the  typhoid 
bacillus,  the  result  being  rather  a  summation  of 
the  intoxication  of  the  two  infections.  Post- 
typhoidal  suppurations  are  often  due  to  the  strep- 
tococcus and  in  many  of  the  metastatic  complica- 
tions (parotitis,  pleurisy,  peritonitis,  meningitis, 
otitis  media)  streptococci  and  staphylococci  have 
been  found.  Pneiimococcus  pneumonia  not  infre- 
quently complicates  typhoid  fever.  A  combined 
infection  of  t^'phoid  and  malaria  is  said  to  occur  in 
the  tropics;  the  complication  is  grave.  T3q3hoid 
and  diphtheria  may  occur  together,  and  typhoid 
may  be  superimposed  on  acute  tuberculosis. 

The  period  of  greatest  susceptibility  to  typhoid  immunity  and 
is   found  from  the  fifteenth  to  the '  twenty-fifth   susceptibility. 
years.     The  resistance  of  infants  and  children  is 
not  satisfactorily  explained.     A  certain  amount  of 
resistance  inherited  from  the  mother  may  persist 


276  INFECTION  AND  IMMUNITT. 

for  some  j'ears  after  birth.  It  is  known  that  anti- 
bodies ma)^  pass  from  the  mother  to  the  fetus 
through  the  phicenta.  In  very  early  life  the  tissues 
may  respond  more  energetically  to  incipient  in- 
fection by  the  rapid  formation  of  typhoid  anti- 
bodies, or  the  phagocytic  cells  may  be  more  active. 
The  conditions  which  render  older  people  less  sus- 
ceptible are  no  better  understood.  A'  loss  of  suit- 
able receptors  may  have  occurred  so  that  the  toxic 
constituents  of  the  bacilli  find  no  anchorage  in  the 
body,  or  the  affinity  between  the  receptors  and  the 
toxic  constituents  may  have  become  less.  The  in- 
dividual during  the  course  of  years  may  have  been 
gradually  immunized  by  the  entrance  of  non- 
pathogenic quantities  of  the  bacilli  into  the  cir- 
culation. That  resistance  to  typhoid  infection  is 
decreased  by  low  nutrition  and  overwork  is  a  long- 
known  fact. 

Natural  and  A  large  amouut  of  protection  is  afforded  by  the 
munity.  hvdrochloric  acid  of  the  gastric  juice,  and  it  is 
reasonable  to  believe  that  suppression  or  an  insuf- 
ficient amount  of  hydrochloric  acid  may  favor  the 
passage  of  living  bacilli  to  the  intestines.  Normal 
human  serum  is  rather  strongly  bactericidal  for 
the  typhoid  bacillus,  and  the  leucocytes  ingest  and 
destroy  it.  Metchnikoff  ascribes  natural  immun- 
ity to  the  action  of  the  microphages. 

Duration  of  The  immunity  which  follows  an  attack  of 
immuniTy*!  typhoid  fcver  is  generally  of  long  duration,  but 
second  attacks  occur  with  some  frequency.  It  has 
been  noted  that  limited  communities  which  have 
experienced  an  epidemic  may  remain  relatively 
free  from  the  disease  over  a  period  of  some  years, 
although  neighboring  districts  are  attacked.  All 
the  susceptible  persons  having  had  the  disease,  a 


TYPHOID  FEVER.  277 

state  of  temporary  regional  immunity  is  created. 
Acquired  immunity  is  characterized  by  an  increase 
of  the  bactericidal  amboceptors,  agglutinins  and 
typhoid  precipitins  in  the  serum.  It  is  com- 
monly believed  that  recovery  is  due  to  the  increase 
of  the  bactericidal  power  of  the  body  fluids,  which 
becomes  most  marked  during  the  later  period  of 
the  disease  or  during  convalescence.  It  seems  cer- 
tain, however,  that  the  new  resistance  persists  be- 
yond the  time  when  the  bactericidal  power  of  the 
serum  has  returned  to  normal,  which  may  take 
place  in  from  one  to  several  years.  The  bacteri- 
cidal power  sinks  rapidly  during  and  following 
convalescence.  However,  the  general  principle  is 
well  established  that,  although  the  antibodies  may 
have  disappeared  entirely,  they  are  reformed  more 
readily  as  a  consequence  of  an  old  infection  (Neis- 
.ser  and  Shiga).  The  tissue  cells  have,  so  to  say, 
been  trained,  and  are  stimulated  by  a  few  micro- 
organisms to  produce  such  a  quantity  of  bacteri- 
cidal amboceptors  that  the  incipient  infection  is 
■overcome.  It  is,  of  course,  understood  that  the 
amboceptors  require  the  aid  of  complement  in  kill- 
ing the  micro-organisms.  A  second  attack  of 
typhoid  fever  usually  is  mild. 
•  Metchnikoff  does  not  deny  that  the  amboceptors 
(fixators)  play  an  important  part  in  acquired  im- 
munity, but  claims  that  the  new  resistance  de- 
pends chiefly  on  an  increase  in  the  phagoc}i;ic 
power  of  the  microphages  (polymorphonuclear  leu- 
cocytes). ■  This  is  not  clear  from  the  clinical 
standpoint  because  of  the  hypoleucocytosis  which 
is  somewhat  characteristic  of  typhoid — a  hypoleu- 
cocytosis caused  chiefly  by  a  disappearance  of  the 
microphages.    It  has  been  suggested  that  our  con- 


Leucocytes. 


27S  IXFECTIOX  AXD  IMMUyiTY. 

elusions  as  to  hypoloiu-ocvtosis  arc  based  on   ex- 
amination  of   the   poriphoval   blood,   whereas   the 
mesenteric    vessels    may    show    hyperleucocytosis. 
Mallory,    however,    found    a    striking    absence    of 
microphages  even  in  tlie  intestinal  vessels.     Con- 
cerning a  theory  that  the  liypcrplasia  of  the  lym- 
phoid organs  serves  as  a  substitute  for  the  hyper- 
leucoc3i;osis,  we  may  recall  the  findings  of  Mallory 
that  this  hyperplasia  is  chiefly  one  of  endothelial 
cells.     The  importance  of  these  endothelial  cells 
for  the  destruction  of  typhoid  bacilli  needs  further 
investigation. 
Prophylaxis.       Prophylaxis    should    begin    with    the    thorough 
disinfection  of  the  stools  and  urine  of  typhoid  pa- 
tients, and  this  should  be  continued  until  they  no 
longer  contain  typhoid  bacilli.     It  is  not   good 
hygiene  to  discharge  a  patient  until  bacteriologic 
examination  of  stools  and  urine  show  them  to  be 
free  from  the  organisms.    It  would  be  difficult  to 
carry  out  this  rigid  precaution  under  all  condi- 
tions, but  at  all  events  the  stools  and  urine  may  be 
disinfected  for  a  reasonable  period,  say  through- 
out convalescence.     There  is  no  sufficient  reason 
for  the  neglect  of  the  bacteriologic  examination  in 
hospital  practice.     There  is  a  growing  sentiment 
that  typhoid  patients  in  hospitals  should  be  iso- 
lated in  wards  or  rooms  in  which  there  is  a  fixed 
routine  for  the  disposal  of  infectious  materials — 
urine,  stools  and  sputum.    Soiled  linen,  the  bath 
water  of  typhoid  patients,  the  remnants  of  food 
and  drink,  and  the  eating  utensils  should  be  dis- 
infected before  removal  from  the  room.     jSTurses 
or  attendants  should  not  eat  or  drink  in  typhoid 
rooms. 


TYI'IIOIIJ  J'/'JVKJC. 


279 


Serum  Therapy 
and  Vaccina- 
tion. 


The  value  of  hexamethylenamine  in  causing  the  Hexamethyi 
disappearance  of  bacilli  from  the  urine  is  now  well  ^"■•«""^- 
known,  and  the  advisability  of  using  the  drug  as 
a  routine  measure  for  public  safety  is  worthy  of 
consideration.  The  room  should  be  kept  free  from 
flies  and  eventually  it  should  be  disinfected,  pref- 
erably by  formalin.  During  an  epidemic,  in  case 
the  water  supply  of  a  community  is  susceptible  to 
contamination  ,all  water  used  for  drinking,  wash- 
ing of  vegetables  and  eating  utensils,  should  be 
boiled,  and  that  used  for  general  cleaning  may  be 
otherwise  disinfected.  The  possibility  of  dust  in- 
fection of  a  house  should  not  be  disregarded. 

There  are  two  methods  of  specific  prophylaxis 
against  typhoid:  1,  the  injection  of  antityphoid 
immune  serum;  2,  preventive  inoculation  with 
killed  cultures  of  the  bacilli.  Antityphoid  serum 
confers  a  fairly  strong  and  immediate  immunity 
which,  however,  is  of  short  duration,  because  of 
the  rapid  elimination  of  the  serum.  Its  use  as  a 
general  preventive,  therefore,  is  not  advocated. 

AVright  has  been  influential  in  showing  the  util- 
ity of  protective  inoculations  against  t3'phoid.  His 
first  experimental  work  was  j)nblished  in  1896. 
Since  that  time  the  inoculations  have  been  carried 
on  extensively  in  British  regiments  in  India  and 
South  Africa.  The  occurrence  of  typhoid  among 
the  inoculated  was  one-half  that  among  the  unin- 
oculated,  and  the  inoculations  reduced  the  mor- 
tality of  the  disease  by  one-half.  The  protection, 
so  far  as  known,  lasts  for  two  or  more  3^ears,  al- 
though in  some  instances  infection  has  occurred  in 
from  three  to  six  months  after  vaccination. 

The  methods  of  preparation  of  the  vaccine  are 
elaborate  in  order  to  insure  sterility  and  standard- 


Wright's 

Method 
and  Results. 


The  Vaccine. 


280  IXFECTIOX  AXD  IMMUXITY. 

■  ization.  Cultures  of  the  baeillus  are  gro^ni  in 
bouillon  for  from  twenty-four  to  forty-eight 
hours,  and  then  sterilized  at  GO  C.  The  contents 
of  several  flasks  are  mixed  in  order  to  obtain  a 
uniform  distribution  of  organisms,  and  standard- 
ization is  then  accomplished  by  a  convenient  meth- 
od of  estimating  the  number  of  bacilli  in  a  cubic 
centimeter  of  the  vaccine.  The  purity  of  the  vac- 
cine is  insured  by  bacteriologic  tests,  and  for  pres- 
ervation carbolic  acid  or  lysol  is  added. 
Effects.  AYriglit  has  abandoned  his  original  method  of 
giving  a  single  injection  and  now  recommends  two 
moderate  doses,  which  are  given  from  eight  to 
fourteen  days  apart.  The  first  dose  includes  a 
quantity  of  vaccine  which  contains  from  750,000,- 
000  to  1,000,000,000  of  bacilli,  the  second  1,500,- 
000.000  to  2,000,000,000.  Wright  finds  that  "the 
inoculation  of  these  quanta  induces  an  ample 
elaboration  of  antitropic  substances  (antibodies) 
without  producing  any  severe  constitutional  reac- 
tion." The  inoculations  increase  the  bactericidal 
and  agglutinating  powers  of  the  serum  and  it  is 
concluded  that  an  increased  resistance  to  typhoid 
intoxication  is  established  because  the  second  in- 
jection causes  milder  symptoms  than  the  first. 
The  phagocytic  power  of  the  leucocytes  is  raised, 
because  of  an  increase  in  the  "opsonic  antitropins" 
(Part  I,  Chapter  XIV).  The  curve  of  the  anti- 
bodies is  like  that  usually  obtained  by  active  im- 
munization with  bacteria,  toxins  or  other  sub- 
stances. Immediately  following  the  inoculation 
there  is  a  decrease  even  of  normal  antibodies.  This 
"negative  phase"  lasts  for  from  one  to  several  days 
and  corresponds  to  a  period  of  increased  suscepti- 
bility.    It  is  quickly  followed  by  a  positive  phase 


Reactions. 


TYPHOID  FEVER.  281 

in  which  the  antibodies  and,  correspondingly,  the 
resistance  increase  rapidly.  When  very  small 
doses  are  administered  the  positive  phase  may  be 
recognized  after  twenty-four  hours  (Wright). 
Large  doses  cause  a  prolonged  negative  phase  and 
are  to  be  avoided. 

Following  injection,  "the  local  symptoms  first  Local 
make  themselves  felt  after  an  interval  of  two  or 
three  hours.  The  effects  then  seen  are  the  develop- 
ment of  a  red  blush  and  more  or  less  serous  exuda- 
tion at  the  site  of  inoculation,  followed  by  some 
lymphangitis  along  the  lymphatics  which  lead,  ac- 
cording as  the  vaccine  has  been  inoculated  above 
or  below  the  middle  line  of  the  trunk,  in  the  direc- 
tion of  the  glands  of  the  axillas  or  of  the  groin. 
.  .  .  Even  severe  inflammation  has  never  led  on 
to  suppuration.''  The  exudate  is  somewhat  hem- 
orrhagic, and  the  pain  moderate  to  severe,  but  not 
of  long  duration.  With  the  technic  as  recom- 
mended at  present,  "the  constitutional  symptoms  General 
are  limited  to  some  headache  and  to  two  or  three 
hours  of  real  malaise.  .  .  .  The  next  day  his 
temperature  comes  down  to  normal,  and  he  feels 
comparatively  well  except  in  respect  to  pain  at  the 
seat  of  inoculation." 

The  adoption  of  antityphoid  inoculation  or  vac-  conditions  for 

,.  n  ,    .  T,.  ,1        Vaccination. 

emation  under  certain  conditions  appears  to  be 
warranted.  Typhoid  never  has  been  a  world  pest; 
hence,  the  occasion  for  universal  vaccination  does 
not  exist,  but  in  the  presence  of  epidemics  so  fre- 
quently seen  in  American  cities  it  will  be  impos- 
sible to  avoid  the  consideration  of  vaccination  as  a 
means  of  protecting  the  uninfected.  The  question 
is  a  pertinent  one  also  for  those  cities  in  which 
typhoid  is  so  extensive  as  to  be  called  endemic. 


282  lMi:VTIOX  AXD  IMMVXITY. 

Mixed  Actjve       It  has  bcoii  suggostccl  that  the  ''negative  phase" 

and    Passive     ,  •!       i       i  ■""  p     ^  •       xi  ,  .„ 

Immunization,  descnoeil  abovc  IS  a  source  ot  danger  m  the  pres- 
ence of  an  epidemic.  The  phase  is  so  short,  how- 
ever, tliat  tlic  danger  is  minimal  and  it  seems 
probabk'  that  the  practice  of  mixed  active  and 
passive  immunization  woukl  eliminate  it  entirely. 
This  is  accomplished  by  the  combined  injection  of 
antit3'^phoid  serum  and  vaccine.  The  serum  as- 
sures a  positive  phase  from  the  start,  and  before 
this  has  subsided,  that  induced  by  the  vaccine  is 
established.  When  specific  serum  is  mixed  with 
the  vaccine  the  local  reaction  is  said  to  be  less 
severe. 

The  products  of  autodigestion  of  typhoid  cul- 
tures have  been  suggested  as  suitable  vaccine 
(Neisser  and  Shiga).  The  local  reaction  is  said 
to  be  mild,  and  the  body  reacts  by  the  formation 
of  bactericidal  amboceptors  and  agglutinins. 

Bactericidal  serums  obtained  by  the  immuniza- 
tion of  horses  with  typhoid  bacilli  have  not  shown 
distinct  curative  properties.  Chantemesse  im- 
munizes horses  with  a  typhoid  "toxin"  which  is 
prepared  by  growing  the  organism  in  a  liquid  cul- 
ture which  contains  an  emulsion  of  splenic  tissue. 
One  cubic  centimeter  of  this  toxin  will  kill  a 
guinea-pig,  a  dose  which  in  comparison  with 
other  bacterial  toxins  is  very  weak.  Chantemesse 
has  used  his  antitoxic  serum  in  the  treatment  of 
more  than  500  cases,  reporting  a  mortality  of 
about  6  per  cent.,  whereas  that  among  untreated 
patients  was  from  10  per  cent,  to  12  per  cent. 
Although  these  figures  indicate  some  value  for  the 
serum  it  has  had  little  trial  outside  of  France. 

McFadyan  and  Eowland  immunize  horses  with 
extracts  of  typhoid  bacilli,  which  have  been  ground 


Serum 
Therapy. 


TYFJIOW  FEVER.  283 

up  while  they  were  kept  in  a  brittle  state  by  the 
temperature  of  liquid  air.  Although  antitoxic  and 
bactericidal  properties  are  claimed  for  the  serum, 
there  is  no  conclusive  evidence  that  it  differs  from 
a  bactericidal  serum  prepared  in  the  ordinary  way. 

Jez  produces  a  high  degree  of  immunity  in  rab-  Preparation 
bits  by  artificial  immunization  with  the  typhoid 
bacillus,  then  prepares  an  extract  from  the  spleen, 
bone  marrow,  brain,  etc.,  of  the  immunized  ani- 
mals. The  extract  is  administered  by  mouth.  Jez 
justifies  this  method,  from  the  fact  that  the  l}Tn- 
phoid  organs  have  been  shown  to  form  typhoid 
antibodies  (Wasserman).  From  the  clinic  of 
Eichorst  and  some  others  favoral)le  reports  con- 
cerning the  remedy  have  been  published.  It  has 
had  no  extensive  use.  The  preparation  is  made  by 
the  Serum  Institute  of  Berne  (Switzerland)  and 
is  expensive. 

The  suggestion  made  by  Fraenkel,  that  typhoid 
patients  be  treated  by  subcutaneous  injections  of 
small  quantities  of  killed  typhoid  bacilli  in  order 
to  hasten  the  formation  of  antibodies  has  been 
kept  alive  through  the  "typhoin"  of  Petruschky, 
but  is  yet  without  much  practical  trial.  Of  a  simi- 
lar nature  is  the  suggestion  of  Richardson,  that 
the  filtrates  of  typhoid  cultures  be  injected. 

The  principles  and  technic  of  the  agglutination  Agglutination 
test  were  described  in  Part  I.  The  serum 
commonly  becomes  agglutinating  on  from  the 
seventh  to  the  tenth  day,  rarely  as  early  as  the 
second  or  third,  and  as  late  as  from  the  twentieth 
to  the  fortieth  day.  The  power  is  highest  during 
convalescence,  when  it  may  agglutinate  in  dilu- 
tions as  high  as  1/5,000  or  higher,  and  from 
that    time    sinks    gradually.     An    agglutinating 


284  INFECTIOX  AND  IMMUNITY. 

•  power  of  1/1()0  has  often  been  found  at  eight' 
months,  and  of  1/50  after  from  seven  and  one-half 
to  eleven  years;  but  the  latter  duration  is  not  the 
rule.  In  performing  the  test  a  scrum  dilution  of 
not  less  than  1  to  -iO,  or  1  to  50  should  be  observed 
as  previously  set  forth. 

The  following  sources  of  error  are  to  be  borne 
in  mind:  Typhoid  fever  occasionally  runs  its 
course  without  the  formation  of  agglutinins;  the 
reaction  may  mysteriously  be  absent  one  day  to 
recur  a  few  days  later,  a  condition  which  indicates 
the  importance  of  repeated  tests;  rather  high  ag- 
glutinating power  for  the  typhoid  bacillus  occa- 
sionally develops  in  other  infections,  as  pneumo- 
nia, meningitis,  icterus,  Weil's  disease,  etc. ;  the 
possibility  of  group  agglutination,  for  the  positive 
elimination  of  which  control  tests  with  related  or- 
ganisms may  be  demanded. 

In  case  negative  results  are  obtained  in  a  sus- 
picious case,  the  reactions  should  be  tried  with  the 
paratyphoid  bacilli. 

The  test  of  the  bactericidal  powers  of  the  serum 
has  been  recommended  as  a  substitute  for  the  ag- 
glutination reaction,  but  the  technic  is  so  much 
more  complicated  that  the  method  will  probably 
not  come  into  general  use. 

For  diagnosis  previous  to  the  formation  of  ag- 
glutinins, blood  cultures  should  be  made  as  de- 
scribed in  a  preceding  paragraph. 

II.    PARATYPHOID  FEVER. 

Paratyphoid       In  1900  Schottmliller  cultivated  from  the  blood 
colon"  Bacilli,  of  fivc  "typhoid"  patients  organisms  which  differ 
from  the  typhoid  bacillus  in  that  they  attack  dex- 
trose with  gas  formation  and  are  not  agglutinated 
conspicuously  by  antityphoid  serum.     Since  that 


PARATYPHOID.  285 

time  many  similar  cases  have  been  reported  and 
two  types  of  the  paratyphoid  bacillus  have  been 
recognized  (SchottmilUer).  Group  B  causes  first 
an  acid  reaction  in  milk  which  changes  to  a  per- 
manently alkaline  reaction  in  about  ten  days, 
whereas  Group  A  causes  permanent  acidity  (Kay- 
ser).  They  resemble  the  typhoid  bacillus  morpho- 
logically, but  culturally  are  more  closely  related  to 
to  Bacillus  enteritidis.  Organisms  which  have 
previously  been  described  as  "paracolon"  bacilli 
(Widal,  Gwyn)  do  not  differ  from  those  which  are 
now  called  paratyphoid  bacilli,  and  the  infections 
caused  by  them  resembled  the  recorded  cases  of 
paratyphoid  fever.  The  term  "paracolon"  should 
no  longer  be  applied  to  them. 

Paratyphoid  fever  occurs  sporadically  or  in  epi-  Epidemiology. 
demic  form,  and  bears  a  close  resemblance  to  mild 
typhoid-like  epidemics  which  have  been  noted  from 
time  to  time,  and  which,  presumably,  are  caused 
by  eating  poisonous  meats.  One  such  epidemic  of 
600  cases  was  caused  in  Switzerland  in  1878  by 
the  meat  of  a  sick  calf;  the  mortality  was  1  per 
cent.  A  still  older  epidemic  (1839)  is  cited,  like- 
wise caused  by  meat.  In  both  instances  the  infec- 
tion eventually  was  carried  from  person  to  person 
by  contact.  A  recent  outbreak  in  Kiel,  proved  to 
be  paratyphoid,  is  assumed  by  Fischer  to  have  been 
caused  by  infected  meat,  on  account  of  the  peculiar 
distribution  of  the  cases  among  the  patrons  of  a 
particular  market.  Kurth  also  attributed  a  small 
epidemic  to  either  uncooked  meat  or  milk.  Fischer 
mentions  50  cases  in  East  Holstein  which  probably 
were  infected  by  the  milk  of  two  cows.  Shortly 
after  the  epidemic  began  the  cows  died  and  para- 
typhoid bacilli  were  cultivated  from  the  muscles. 


iM'EcTiox  A\n  fMMrxrrr. 


Characteristics 
of  the  Disease. 


Excretion,  Re- 
sistance and 
Distribution. 


spleen,  liver  and  intestines.  De  Feyl'er  eites  an  in- 
stance iu  wliieh  the  disease  apparently  was  trans- 
mitted through  the  water  of  a  stream  in  whieh  the 
clothing  of  the  first  patients  had  heen  washed.  In 
another  instance,  a  regimental  infection  was  traced 
to  the  discharges  of  a  single  soldier,  the  water  sup- 
ply having  become  contaminated  through  a  defec- 
tive water  closet. 

Paratyphoid,  like  typhoid  fever,  is  accompanied 
by  an  enlarged  spleen  and  many  rose  spots.  Al- 
though severe  symptoms  may  be  present  for  a  time, 
the  course  of  the  disease  usually  is  mild  and  the 
mortality  is  low.  The  incubation  period  approxi- 
mates that  of  typhoid.  In  the  few  cases  which 
have  come  to  autopsy  the  intestinal  lesions  have 
varied  from  a  mild  ileocolitis  with  an  intact  mu- 
cous surface  to  a  condition  of  superficial  ulcera- 
tion. The  involvement  of  Peyer's  patches  and  the 
solitary  follicles  which  is  so  characteristic  of  ty- 
phoid is  absent,  although  these  structures  may  be 
moderately  swollen.  The  mesenteric  lymph  glands 
are  not  markedly  involved  and  there  is  little  pro- 
liferation of  the  lymphoid  or  endothelial  cells 
(Wells  and  Scott).  The  disease  has  no  specific 
anatomic  lesion. 

The  organisms  are  found  in  the  blood  and  vari- 
ous organs,  in  the  rose  spots,  urine  and  feces  of  the 
patients.  Practically  nothing  is  Imown  of  the  oc- 
currence of  the  bacilli  outside  the  body.  Because 
of  their  presence  in  the  stools  and  urine  of  the  pa- 
tients, the  methods  of  dissemination  and  infection 
doubtless  are  similar  to  those  concerned  in  typhoid. 
The  bacillus  is  said  to  have  a  marked  resistance  to 
heat,  withstanding  60°  C.  for  30  minutes  and 
not    all    cells    hems:    killed    durina-    one    liouv    at 


PARATYrilOID.  287 

this  temperature.  This  may  explain  the  fact  that 
the  virus  is  not  alwa_ys  killed  by  cooking  the  meat. 
The  organism  probably  has  a  wide  distribution 
because  of  the  occurrence  of  the  infection  in  vari- 
ous parts  of  the  world. 

The  toxicity  of  the  bacilli  depends  on  the  exist- 
ence of  a  fixed  endotoxin;  a  soluble  toxin  is  not 
produced. 

The  principles  of  prophylaxis  against  typhoid 
also  apply  to  paratyphoid  fever,  with  the  addition 
that  in  the  latter  disease  the  possibility  of  meat  in- 
fection must  be  kept  in  mind. 

The  serums  of  patients  and  immunized  animals 
acquire  bactericidal  and  agglutinating  powers  for 
the  organism. 

There  is  no  serum  therapy  for  the  infection,  nor 
has  the  occasion  arisen  to  attempt  vaccination. 

Serum  from  a  paratyphoid  patient  may  aggluti-  Agglutination 
nate  the  homologous  bacillus  in  a  dilution  of  cultures. 
1/1000  or  1/2000  or  more  (E.  H.  Ptuediger), 
whereas  the  typhoid  bacillus  is  agglutinated  only 
in  low  dilutions  by  the  same  serum.  How- 
ever, bacillus  A  and  bacillus  B  are  not  identical 
in  their  agglutinable  properties;  in  this  respect 
it  is  stated  that  the  latter  is  more  closely  re- 
lated to  the  typhoid  bacillus  than  the  former. 
The  agglutination  test  is  said  to  have  a  higher 
diagnostic  value  than  the  Gruber-AVidal  reaction 
in  typhoid,  a  stronger  agglutinating  power  being 
developed  in  the  serum  of  the  patient.  JsTever- 
theless,  the  formation  of  coagglutinins  may  render 
the  test  confusing  if  proper  serum  dilution  is  not 
practiced.  Conclusions  should  not  be  attempted 
until  the  test  has  been  performed  with  both  strains 
of  the  paratyphoid  bacillus  and  with  the  tj^phoid 


288  IXFECTIOy  AXD  IMMUXITY. 

■  bacillus.  As  iu  typhoid,  early  diagnosis  may  be 
best  accomplished  by  bacteriologic  examination  of 
the  blood. 

III.    ACUTE    EPIDEMIC    DYSENTERY. 

In  addition  to  amoebic  dysenter}^  we  have  be- 
come familiar  with  an  acute  dysenteric  infection 
which  appears  epidemically  in  both  tropical  and 
temperate  climates,  and  prevails  especially  in  the 
summer  months.  Such  epidemics  occur  extensively 
in  Japan,  where  the  mortality  may  be  24  per  cent. ; 
in  the  Philippines,  United  States,  Germany  and 
other  European  countries.  In  industrial  settle- 
ments in  Germany  the  mortality  is  about  10  per 
cent.  (Kruse).  The  incubation  period  may  be  as 
short  as  two  or  three  days.  In  mild  cases  the  pa- 
tient may  recover  in  from  four  to  eight  days, 
whereas  severe  cases  last  from  two  to  four  weeks, 
and  may  terminate  fatally.  Occasionally  the  in- 
fection lasts  suflBciently  long  to  be  considered 
chronic. 
Two  Types  In  1898,  Shiga,  basing  his  conclusions  on  posi- 
of  Bacilli.  |.-^g  results  with  the  agglutination  test  and  on  the 
constant  presence  of  the  organism  in  the  stools  of 
the  infected,  identified  as  the  cause  of  the  disease, 
in  Japan,  a  microbe  which  is  Icno^Ti  as  Bacillus 
dysenterm  (Shiga).  Flexner,  in  1900,  made  simi- 
lar observations  on  epidemic  dysentery  in  Manila, 
and  his  organisms,  or  one  of  them,  differing  slight- 
ly from  that  of  Shiga,  is  called  Bacillus  dysentcrioe 
(Flexner),  or  the  Flexner-Harris  bacillus,  Harris 
being  the  name  of  a  patient  from  whom  this 
typical  strain  was  cultivated.  Kruse  (1901)  found 
both  the  Shiga  and  Flexner  types  in  Germany, 
needlessly  giving  the  name  of  "pseudodysentory" 
bacilli  to  the  latter.    In  this  countrv  similar  organ- 


ACUTE  DYSENTERY.  289 

isms  liave  been  found  as  the  caiise  of  institutional  summer 
dysentery  by  Vedder  and  Duval,  of  summer  diar-  Diarrheas. 
rheas  of  infants  by  Duval  and  Bassett,  and  by  Wol- 
stein.  It  is  the  belief  of  Vedder  and  Duval  that 
acute  dysentery,  the  world  over,  "whether  sporadic, 
institutional  or  epidemic,  is  caused  by  the  dysen- 
tery bacillus."  We  must  note,  however,  that  the 
organism  is  not  found  in  all  cases  of  clinical  dys- 
entery, even  by  skilled  bacteriologists.  "Clinically,, 
24  of  our  97  cases  in  which  the  dysentery  bacilli 
were  found  did  not  differ  from  the  cases  of  ileocoli- 
tis in  which  the  dysentery  bacilli  were  not  found.'" 
(Weaver  and  others.)  It  seems  certain,  neverthe- 
less, that  Bacillus  dysenterice  is  the  most  impor- 
tant cause  of  acute  dysentery.  It  rarely  occurs  in 
the  stools  of  healthy  individuals. 

The  organisms  of  Shiga  and  Flexner  differ  in 
their  actions  on  sugars  (i.  e.,  in  their  acid-forming 
powers)  and  in  their  agglutinability ;  the  "Flex- 
ner" type  is  the  stronger  acid-former.  An  artificial- 
ly produced  immune  serum  which  is  specific  for  one 
organism  has  rather  higher  agglutinating  and  bac- 
tericidal powers  for  the  corresponding  type,  but 
low  for  the  other.  In  this  country  the  "Flexner" 
bacillus  is  much  more  common  than  that  of 
"Shiga,"  but  here  and  abroad  both  types  are  met, 
and  sometimes  in  the  same  individual.  Several 
other  organisms  have  been  cultivated  from  dysen- 
teric patients,  but  the  variations  from  these  two 
types  are  slight.  All  are  certainly  very  closely  re- 
lated. 

The  organism  is  somewhat  thicker  than  the  ty-  characteristics 
phoid    bacillus,    but    probably    is    non-motile,    al-  "  *  ^  ^^^'  '" 
though  Vedder  and  Duval,  in  opposition  to  others 
(Lentz),  claim  to  have  demonstrated  flagella.     It 


200  IXFJJCTIOX  A\D  IMMUXITY. 

often  shows  a  polyinorphoiis  appearance  in  cul- 
tures, but  forms  no  spores.  It  is  Gram-negative. 
It  lives  for  from  12  to  17  days  when  dried 
(Pfuhl)  ;  direct  sunlight  kills  it  in  30  minutes, 
1  per  cent,  carbolic  acid  in  30  minutes,  5  per  cent, 
carbolic  acid  plus  corrosive  sublimate  (1/2000) 
almost  instantaneously.  It  is  thought  that  it  may 
live  over  winter  and  cause  fresh  outbreaks  in  the 
spring  (Kruse). 
Distribution       Thc  bacillus  is  fouud  only  in  the  stools  of  the 

in  the  Body.     ■     n      ,    j     •       ,r.  ,  ,         . 

infected,  m  the  mucous  or  muco-hemorrhagie  por- 
tions of  which  it  exists  almost  in  pure  culture,  few 
colon  bacilli  being  in  the  immediate  vicinity;  it 
has  not  been  found  in  the  blood  or  iirine.  In  fatal 
cases,  Shiga  found  it  only  in  the  intestinal  ulcers 
and  swollen  lymphoid  structures  and  in  the  mesen- 
teric lymph  glands.  Flexner  mentions  its  occur- 
rence in  the  liver.  The  organism,  if  it  reaches  the 
circulation  at  all,  either  does  so  in  small  quantities, 
or  is  rapidly  destroyed  by  the  blood.  The  infection 
resembles  cholera,  but  differs  from  typhoid  and 
paratyphoid  in  this  respect.  An  observation  by 
Markwald  (cited  by  Lentz)  indicates,  however, 
that  the  bacilli  may  reach  the  circulation.  A 
woman  sick  with  dysentery  gave  birth  to  a  child, 
which  died  within  a  few  hours.  Dysenteric  changes 
were  found  in  the  intestines,  and  the  bacillus  of 
dysentery  was  cultivated  from  the  diphtheritic  de- 
posits on  the  intestines,  from  the  meconium  and 
from  the  heart's  blood.  The  organisms  must  have 
reached  the  child  through  the  placenta  from  the 
circulation  of  the  mother. 
Lesions.  The  intestinal  lesions  vary  from  a  simple  in- 
flammatory hyperemia  to  rather  extensive  superfi- 
cial  necrosis    (diphtheritic  inflammation),   which 


ACUTE  DYSENTERY.  291 

rarely  extends  below  the  submucosa.  Such  foci 
are  said  to  be  the  most  marked  in  the  descending 
colon  and  sigmoid  where  mechanical  injury  is 
more  likely  to  occur.  The  necrotic  areas  separate 
by  sloughing,  leaving  superficial  ulcers.  The  lym- 
phoid follicles  ai'e  swollen  and  infiltrated  with 
polymorphonuclear  leucocytes,  which  also  accumu- 
late in  the  dilated  lymph  spaces  of  the  intestinal 
wall.  The  ileum  is  so  commonly  involved  that  the 
condition  is  called  an  ileocolitis.  Conspicuous 
changes  are  not  found,  in  the  mesenteric  glands  or 
spleen.  The  liver  and  kidneys  commonly  show 
parenchymatous  degenerations. 

The  dysentery  bacillus  is  highly  toxic.  Subcu-  Toxicity  of 
taneous  injections  of  killed  cultures  produce  in 
man  a  more  profound  reaction  than  the  organism 
of  either  cholera  or  typhoid.  Ordinary  laboratory 
animals  are  so  susceptible  that  they  are  immunized 
with  difficulty;  the  horse  is  less  susceptible.  The 
toxicity  of  the  organism  apparently  depends  on  an 
intracellular  toxin  (an  endotoxin)  rather  than  on 
a  soluble  toxin.  When  living  or  killed  cultures 
are  submitted  to  autodigestion  in  salt  solution 
(Conradi,  Msser  and  Shiga),  or  when  bouillon 
cultures  are  allowed  to  grow  for  30  days,  the 
liquids  are  found  to  be  toxic  after  the  organisms 
are  removed.  In  both  instances  this  toxicity  prob- 
ably depends  on  the  liberation  of  endotoxins.  The 
question  as  to  whether  the  bacillus  in  the  intes- 
tines produces  a  soluble  toxin  which  is  absorbed  by 
the  lymphatics,  is  undetermined.  It  seems  more 
probable  that  the  conditions  are  analogous  to  those 
of  cholera,  intoxication  resulting  from  the  libera- 
tion of  endotoxins  by  the  solvent  action  of  the  tis- 
sue fluids  or  cells  on  the  bacilli.    Dysenteric  symp- 


292  IXFECTIOX  AXD  IMMUyiTY. 

•  toiiis  arc  not  producod  in  animals  by  feeding  the 
organisms. 
Dissemination       TliG  stools  of  the  patient  are  the  only  known 
and  Infection,  j^q^^j.^.^  ^f  ^]^q  organism  and  it  continues  to  be  ex- 
creted  during  convalescence.      Latent   or  chronic 
cases  are  a  source  of  danger  to  a  community.     Al- 
thougli   the  conditions  outside   the   body   are   not 
favorable  for  the  growth  of  the  organism,  it  may 
remain  living  and  virulent  for  several  months.  The 
methods  of  infection  appear  identical  with  those 
seen  in  typhoid.     Water  infection  seems  certain, 
and  indirect  transmission  is  acomplished  by  con- 
tact with  the  discharges.     The  best  examples  of 
contact  infection   are  found  in  institutional   epi- 
demics. 
Prophylaxis       The  first  esscutial  for  prophylaxis  is  correct  di- 
*"*' tibli^ity!  agnosis,  for  which  the  agglutination  test  and  bac- 
teriologic  examination  of  the  stools  are  essential. 
Disinfection  and  other  precaiitions  should  be  prac- 
ticed as  rigidly  as  in  tjqDhoid.    The  patient  should 
not  be  discharged  until  the  stools  are  free  fi'om 
•    dysentery  bacilli. 

Poorly  nourished  individuals  are  particularly 
susceptible  to  infection,  and  among  them  the  mor- 
tality is  high.  The  disease  is  most  common  among 
young  children,  old  people,  and  those  who  are  con- 
fined in  institutions.  The  conditions  in  Japan, 
however,  where  from  June  to  December  of  one  year 
nearly  90,000  were  attacked,  and  in  Germany, 
where  severe  epidemics  occur  in  industrial  com- 
munities, indicate  that  susceptibility  is  quite  gen- 
eral. Digestive  disturbances  and  enteritis  from 
other  causes  are  said  to  be  predisposing  factors. 
The  normal  serums  of  man  and  animals  have  vei-y 
little  l)actoricidal  power  for  dysentery  bacilli. 


ACUTE  DYFiENTERY.  293 

The  subject  of  acquired  immunity  to  dysentery  immunity. 
is  hardly  on  a  satisfactory  basis.  The  serum  of 
convalescents  shows  a  distinct  bactericidal  power 
for  the  organism,  and  there  is  good  reason  to  be- 
lieve that  the  acquired  immunity  persists  for  some 
time  after  the  disappearance  of  the  bactericidal  am- 
boceptors, an  event  which  takes  place  rather  early. 
As  in  typhoid,  animals  which  through  immuniza- 
tion have  once  been  stimulated  to  produce  anti- 
bodies, form  them  much  more  readily  on  the  occa- 
sion of  a  subsequent  inoculation.  This  acquired 
facility  in  producing  antibodies  may  be  a  factor  in 
acquired  immunity.  By  immunizing  horses, 
serums  of  rather  high  protective  power  have  been 
obtained.  Kruse  prepared  a  serum  of  which 
1/80000  gram  would  save  a  guinea-]3ig  from  a  dose 
of  the  bacilli  which  killed  a  control  in  20  hours. 
It  is  assumed  that  the  protective  power  of  this 
serum  is  due  to  its  bactericidal  action.  The  anti- 
toxic serum  which  Eosenthal  prepared,  by  immun- 
izing with  30  days'  old  bouillon  cultures,  protected 
not  only  against  the  toxin,  but  also  against  the 
bacilli ;  and  conversely  an  antibacterial  serum  pro- 
tected against  the  toxin  (cited  by  Lentz).  Such 
results  leave  us  very  much  in  doubt  as  to  the  exist- 
ence of  a  true  antitoxic  serum. 

The  value  of  protective  inoculations  is  not  well  vaccination 
established.  Shiga  at  one  time  practiced  mixed  Therapy!™ 
active  and  passive  immunization  (bacilli  plus  im- 
mune serum)  on  10,000  individuals.  This  did  not 
decrease  the  number  of  infections,  although  a  lower 
mortality  resulted.  Shiga  claims  that  the  thera- 
peutic use  of  his  serum  reduces  the  mortality  to  one- 
third  that  of  the  untreated.  The  serum  of  Kruse, 
and  also  that  of  Eosenthal,  are  said  to  be  cura- 


294  IXFECTIOX  AND  IMMUNITY. 

.  tive;  the  discharges  rapidly  decrease  in  number 
and  the  course  of  the  disease  is  shortened.  In  the 
hands  of  the  Eockefeller  Institute,  antidysentery 
serum  proved  of  no  distinct  value. 
Agglutination.  The  agglutination  reaction  with  the  serum  of 
patients  shows  great  variability.  It  is  sometimes 
absent  in  spite  of  the  presence  of  bacilli  in  the 
stools,  and  often  disappears  rapidly  during  con- 
valescence (in  two  weeks  occasionally).  It  is  rarely 
as  high  as  in  typhoid.  In  infantile  diarrheas  ag- 
glutinins appear  at  about  the  end  of  the  first  week 
of  illness  (Duval  and  Bassett).  Evidently  mild 
cases  in  which  the  course  of  the  disease  is  from 
four  to  eight  days  may  not  be  recognized  by  means 
of  the  agglutination  reaction  before  the  period  of 
convalescence.  In  chronic  cases  the  agglutinating 
power  may  persist  for  three  or  four  months.  No 
reaction  was  obtained  with  the  typhoid  bacillus. 
Kruse  considers  the  reaction  diagnostic  when  it 
occurs  in  a  dilution  of  1/50 ;  Pfuhl,  1/30.  Strong 
co-agglutinins  for  other  organisms,  i.  e.,  above 
1/50,  have  not  been  observed  (Lentz).  The  tests 
should  always  be  performed  with  both  the  "Shiga" 
and  "Flexner"  types,  as  the  two  have  not  identical 
agglutinable  properties,  and  either  organism  may 
be  the  cause  in  a  given  instance.  The  absence  of 
the  reaction  does  not  exclude  a  dysenteric  infec- 
tion positively.  Bacteriologic  examination  of  the 
stools  is  important,  often  necessar}',  for  early  diag- 
nosis. 

IV.    MEAT  POISONING  BY  BACILLUS  ENTERITIDIS. 

Botulism  as  a  special  form  of  meat  poison- 
ing and  the  occasional  production  of  paratyphoid 
by  infected  meats,  have  been  mentioned.  In 
addition  to  these,  more  or  less  extensive  epidemics^ 


BACILLUS  ENTERITIDIB.  295 

supposed  to  be  due  to  ptomains  which  were  found 
in  putrid  meat,  have  occurred  not  infrequently. 
It  is  now  well  established  that  most  epidemics  of 
this  character  are  caused  by  pathogenic  Ijacteria 
which  are  present  in  the  meat,  whereas  putrid  de- 
composition of  the  latter  is  an  unessential  incident. 

Gartner,  in  1888,  had  the  opportunity  of  study-  Bacillus 
ing  an  epidemic  caused  by  the  meat  of  a  cow  which  tntentidis. 
had  been  slaughtered  in  extremity.  The  symptoms 
differed  from  those  of  botulism  or  paratyphoid,  as 
described  below.  He  obtained  from  the  muscle  and 
spleen  of  the  cow,  and  from  the  spleen  of  a  man 
who  had  been  fatally  poisoned,  an  organism  which 
has  since  been  loiOAvn  as  Bacillus  enteritidis  ( Gart- 
ner). The  same  bacillus,  or  organisms  which  re- 
semble it  closely,  have  been  obtained  repeatedly 
during  similar  epidemics,  both  from  the  suspected 
meat  and  from  the  organs  in  fatal  cases  (intes- 
tines, blood,  spleen,  etc.).  Drigalski,  from  a  com- 
parative study  of  several  strains  which  had  been 
obtained  from  different  sources,  concluded  that 
all  are  members  of  a  closely  related  group  of  or- 
ganisms, the  group  of  Bacillus  enteritidis.  His 
conclusions  were  based  on  cultural  properties  and 
agglutination  tests. 

The  typical  organism  is  a  short  rod,  often  ovoid 
in  shape,  possesses  from  four  to  twelve  long  flag- 
ella  and  has  moderate  motility.  It  ferments  vari- 
ous sugars  and  is  not  stained  by  Gram's  method. 
Variations  among  individual  strains  need  not  be 
discussed  here. 

According  to  v.  Ermengem,  and  also  Drigalski,  Pathogenicity. 
its  pathogenicity  depends  on  the  elaboration  of  a 
soluble    but   heat-resistant    toxin.      Bouillon   cul- 
tures twelve  days  old,  in  which  the  bacteria  have 


290  IXFECTIOX  AXD  IMMUXITY. 

been  killed  by  heat,  also  similar  cultures  from 
which  the  bacteria  have  been  removed  by  filtration, 
are  toxic  for  mice  and  guinea-pigs  (Drigalski).  It 
is  noteworthy,  however,  that  relatively  large  quan- 
tities of  the  bouillon  were  necessary  to  kill  guinea- 
pigs  (4.0  c.c.)  which  is  in  contrast  to  the  toxins  of 
diphtheria  and  tetanus.  The  rapidity  with  which 
sj-mptoms  develop  following  the  ingestion  of  in- 
fected meat  is  a  further  indication  of  the  exist- 
ence of  this  soluble  toxin,  which,  it  would  seem,  is 
formed  in  considerable  quantities  in  the  meat. 
Symptoms  occasionally  develop  so  quickly  as 
to  suggest  some  strong  metallic  poisoning.  With- 
in a  few  hours  vomiting,  violent  diarrhea  and 
colicky  pains  set  in,  followed  by  more  or  less 
collapse,  weakness,  headache  and  not  imcom- 
monly  by  erythematous,  urticarial  or  herpetic 
eruptions.  Fever  is  absent  or  inconspicuous. 
The  mortality  is  not  high,  from  2  to  5  per  cent. ; 
convalescence  is  said  to  be  slow.  ISTephritis  and 
catarrhal  pneumonia  have  been  noted  as  sequelae. 
Autopsy  shows  the  anatomic  changes  of  an  acute 
gastroenteritis,  sometimes  of  hemorrhagic  charac- 
ter, with  swollen  Pe5'er's  patches;  the  large  intes- 
tine is  not  greatl)'"  involved.  The  spleen  may  be 
swollen  and  the  kidneys  degenerated.  The  ana- 
tomic findings  are  not  specific. 
Sources  of  It  has  been  shown  in  numerous  instances  that 
the  cattle  or  horses  (Drigalski)  which  furnished 
the  meat  were  sick  with  an  intestinal  or  general 
infection  with  Bacillus  enteritidis  before  they  were 
slaughtered.  "In  a  very  large  number  of  cases  it 
can  be  demonstrated  that  the  animals  from  which 
the  meat  was  taken  had  been  slaughtered  in  ex- 
tromitv  or  had   died   recentlv.   and,   indeed,   that 


Infection. 


BACILLUS  ENTERITIDL^.  297 

they  had  (in  certain  instances)  died  hefore  they 
could  be  slaughtered.  Most  often  they  suffer  from 
septic  inflammatory  processes  or  from  traumatic, 
puerperal  or  other  sorts  of  septicemia,  or  from 
other  ill-defined  pathologic  conditions  which  are 
accompanied  by  symptoms  of  enteritis  or  intestinal 
or  pulmonary  inflammations."  (v.  Ermengem.) 
Subsequent  infection  of  the  meat  by  Bacillus  en- 
teritidis,  i.  e.,  after  slaughtering,  has  not  been 
noted. 

The  organism  occurs  in  the  blood  and  various  Growth  in 
organs  of  infected  animals  and  man.  Poisoning  ^  ^  ' 
most  commonly  arises  when  the  meat  has  been 
kept  for  several  days,  which  usually  is  the  case  by 
the  time  it  is  made  into  some  form  of  sausage.  In 
the  meantime  the  bacilli  have  proliferated  and  ad- 
ditional toxin  has  been  produced.  In  at  least  one 
instance  a  certain  number  of  patients  who  ate  the 
meat  while  it  was  fresh  suffered  moderate  or  no 
intoxication,  whereas  those  who  ate  it  several  days 
later  became  violently  ill.  In  an  epidemic  caused 
by  horse  meat  Drigalski  found  that  "only  those 
persons  suffered  from  intoxication  who  ate  the 
meat  after  it  had  lain  for  eight  days  or  more." 

The  micro-organism  is  very  resistant  to  heat  Toxin  in 
and  the  temperature  which  is  attained  in  ordinary 
cooking  may  not  be  sufficient  to  kill  the  bacteria 
which  are  remote  from  the  surface.  Even  in  the 
event  that  the  meat  has  been  thoroughly  sterilized, 
the  heat-resistant  toxin  may  be  present  in  suffi- 
cient quantity  to  cause  the  intoxication.  N'ot 
much  is  Imown  concerning  the  distribution  of 
Bacillus  enteritidis.  v.  Ermengem  suspects  that 
it  may  be  a  factor  in  poisoning  by  oysters  and  fish, 
but  this  remains  undetermined. 


298 


IXFECTIOX  AXD  IMMUNITY. 


Agglutinins.  The  blood  acquires  specific  agglutinins  during 
the  course  of  infection.  Even  eight  days  after  the 
beginning  of  sjonptoms  agglutination  may  be  ob- 
tained in  dilutions  varying  from  1/200  to  1/4000. 
The  agglutinins  disappear  very  rapidly.  Working 
with  artificially  prepared  immune  serum,  Drigal- 
ski  determined  the  existence  of  coagglutinins  for 
typhoid  and  paratyphoid  bacilli. 

AYe  should  bear  in  mind  the  likelihood  that 
meats  poisoned  with  Bacillus  enterltidis,  as  well  as 
by  paratyphoid  bacilli,  may  be  encountered  in 
America,  as  well  as  in  foreign  countries. 

V.    BACILLUS   COLI    COMMUNIS. 

Bacillus  coll  communis.  Bacterium  coli  com- 
mune, or  the  colon  bacillus,  is  the  type  of  a  large 
group  of  organisms  the  members  of  which  show 
individual  differences,  but  possess  certain  domi- 
nant features  in  common.  The  typical  colon  bacil- 
lus ferments  various  sugars,  with  the  production  of 
gas,  is  a  strong  acid  producer  and  curdles  milk.  It 
is  flagellated,  has  moderate  motility  and  does  not 
stain  with  Gram's  method.  One  type  or  another 
is  the  normal  inhabitant  of  the  intestinal  tract  of 
many  animals,  and,  although  the  organisms  are 
widely  disseminated  in  nature,  their  occurrence  is 
related  directly  or  indirectly  to  the  distribution  of 
feces. 
Resistance.  Its  Optimum  temperature  for  growth  is  37°  C, 
and  above  46°  C.  it  does  not  proliferate.  It  is 
killed  at  a  temperature  of  from  60°  to  61°  C.  in 
from  five  to  fifteen  minutes;  it  is  not  killed  by 
such  low  temperatures  as  from  — 20°  to  — 24°  C. 
It  resists  absolute  desiccation  for  periods  var3dng 
from  a  few  days  to  several  months  (different  ob- 
servers).    Direct  sunlight  kills  99  jDer  cent,  of  the 


COLON  BACILLUS.  299 

germs  in  two  hours  (Billings  and  Peckham),  and 
they  are  very  susceptible  to  ordinary  antiseptics. 
The  normal  serums  of  many  animals  are  bacterici- 
dal for  the  colon  bacillus. 

Escherich;,  a  noted  authority  on  this  organism, 
lays  down  the  principle  that  that  strain  which  may 
be  cultivated  from  the  feces  of  the  nursing  child 
should  be  considered  as  the  typical  Bacterium  coli 
commune,  maintaining  that  a  constant  type  of  or- 
ganism is  found  under  these  conditions.  It  is  said 
to  occur  here  in  relatively  pure  culture. 

Within  a  very  short  time  after  birth  the  organ-  Distribution  in 
ism  is  found  in  the  intestines  of  infants,  and  its  **'®  "destines. 
method  of  entrance  has  been  the  subject  of  much 
discussion.  In  view  of  its  ready  dissemination  it  is 
not  difficult  to  conceive  of  many  circumstances 
which  favor  its  entrance.  Having  once  reached 
the  intestines,  it  finds  there  its  optimum  conditions 
for  growth.  The  small  intestines  in  man  are 
rather  free  from  colon  bacilli  and  other  organisms 
as  well.  This,  perhaps,  is  due,  to  some  extent,  to 
the  alkalinity  of  the  medium  and  to  the  rather 
rapid  flow  of  the  intestinal  contents  at  this  point. 
The  colon  bacillus  reaches  its  maximum  develop- 
ment in  the  large  intestine,  where,  in  fact,  the 
whole  bacterial  flora  of  the  intestines  is  most  con- 
centrated. 

In  view  of  the  fact  that  the  colon  bacillus  is  a  Normal 
normal  inhabitant  of  the  intestines,  the  conception 
has  occurred  to  many  that  it  may  be  of  distinct 
value  to  the  economy,  either  because  of  the  action 
it  has  on  certain  foods  (splitting  of  carbohy- 
drates), or  because  in  some  obscure  way  it  in- 
fluences favorably  the  assimilation  of  foods,  or  in 
that  it  antagonizes  other  bacteria  of  distinct  patho- 


300  INFECTION  AND  IMMUNITY. 

genie  powers  wliicli  also  exist  normally  in  the  in- 
testines or  reaeh  them  through  accident.  This  is 
not  the  place  to  consider  these  questions  in  detail, 
and  the}'  are  on  none  too  definite  a  basis.  It  may. 
be  stated,  however,  that  the  colon  bacillus  and  an- 
other closely  related  organism.  Bacillus  lactis  aero- 
gencs,  distinctly  antagonize  the  action  of  certain 
proteol}i;ic  bacteria  which  appear  to  be  associated 
with  the  putrid  decomposition  of  milk  and  other 
proteid-containing  foods.  Bacteria  of  the  latter 
type  exist  in  the  intestines.  Unsterilized  milk  has 
a  natural  resistance  to  putrid  decomposition,  and 
sterilized  milk  which  contains  the  colon  bacillus  or 
Bacillus  lactis  aerogenes  has  a  similar  resistance. 
These  two  bacteria  flourish  in  the  presence  of  car- 
bohydrates, which  they  decompose  with  the  liberal 
formation  of  acids,  and  through  these  acids  they 
"limit  intestinal  putrefaction  and  influence  (fa- 
vorably) pathologic  processes  which  are  caused  or 
maintained  by  the  existing  "^alkaline  fermenta- 
tion'"  (Escherich  and  Pfaundler).  That  the  or- 
ganisms in  question  antagonize  the  action  of  putre- 
factive bacteria  has  been  shown  in  test-tube  experi- 
ments (Hirschler). 
Pathogenicity.  Since  the  time  that  Emmerich  upheld  the  colon 
bacillus  (or  a  colon-like  microbe)  as  the  cause  of 
Asiatic  cholera  (1885),  opinion  as  to  the  patho- 
genic powers  of  the  organism  has  undergone 
many  fluctuations.  Following  Koch's  demonstra- 
tion of  the  vibrio  of  cholera  as  the  etiologic  factor 
in  cholera,  the  colon  bacillus  was,  so  to  say,  re- 
pressed as  a  pathologic  agent.  Later,  and  especially 
in  France,  great  significance  was  again  attached  to 
it.  The  condition  still  shows  a  great  deal  of  chaos, 
although,  on  account  of  more  refined  technic  and 
the  elimination  of  other  organisms,  as  the  dysen- 


COLOIi  BACILLUS.  301 

tery  and  paratyphoid  bacilli  and  Bacillus  enteriti- 
dis,  from  the  colon  group  proper,  we  are,  perhaps, 
^on  the  way  to  a  more  satisfactory  understanding 
of  the  pathogenicity  of  this  organism.  Although 
certain  authors  hold  at  the  present  time  that  the 
colon  bacilli  which  normally  inhabit  the  intes- 
tines are  devoid  of  virulence,  such  a  radical  posi- 
tion is  open  to  question.  Avirulent  strains  have 
often  been  encountered,  however. 

As  harmless  as  the  colon  bacillus  appears  to  be  virulence 
when  confined  in  the  intact  intestines,  its  viru- 
lence for  animals,  although  low,  has  been  demon- 
strated in  many  instances.  A  bouillon  culture  of 
the  average  bacillus  which  has  grown  for  from  one 
to  two  days,  and  when  freshly  cultivated  from  the 
stools,  causes  the  death  of  a  300  to  400  gram 
guinea-pig  in  two  or  three  days,  when  given  intra- 
peritoneally  in  a  dose  of  from  2  to  3  c.c.  Subcu- 
taneous inoculations,  the  feeding  of  cultures,  their 
introduction  into  the  bladder  and  biliary  passages 
induce  inflammatory  jarocesses.  It  is  stated 
(Escherich)  that  whether  the  cultures  are  intro- 
duced into  the  skin,  peritoneum  or  vessels,  symp- 
toms of  severe  gastroenteritis  are  produced,  not 
unlike  Asiatic  cholera.  This  fact  doubtless  in- 
fluenced Emmerich  in  considering  the  organism  as 
the  cause  of  cholera.  The  general  symptoms  are 
those  of  an  acute  febrile  intoxication. 

The  organism  is  most  pathogenic  when  freshly 
cultivated,  and  soon  loses  its  virulence  after  re- 
peated transplantations.  As  in  the  case  of  some 
other  bacteria,  virulence  may  be  re-established  by 
"passage"  through  suitable  animals. 

The  cultivation  of  the  colon  bacillus  from  the 
blood  and  organs  of  man  at  autopsy  has  not  the 


302  IXFECTIOX  A\D  IMMUNITY. 

viruieoce  significance  Avhich  Avas  once  attached  to  it.  It  has 
been  recognized  that  the  colon  bacillus  in  particu- 
lar, and  less  commonly  other  intestinal  organisms,, 
may  enter  the  circulation  a  short  time  before  death, 
at  a  time  when  resistance  is  very  low,  and  may 
obtain  the  general  distribution  which  is  so  often 
encountered  at  autops}';  this  is  the  so-called  "ago- 
nal invasion,"  which  may  occur  without  much  re- 
gard to  the  primary  cause  of  death.  The  condi- 
tions which  favor  agonal  invasion  remain,  to  a 
large  extent,  obscure.  Distinct  defects  of  the  in- 
testinal mucosa  probabl}''  are  not  essential,  al- 
though this  view  has  its  representatives.  In  states 
of  low  vitality  in  which  resistance  to  infection  is 
decreased  (disappearance  of  complement!),  the  or- 
ganisms find  conditions  favorable  to  proliferation 
when  they  have  once  reached  the  circulation.  In 
spite  of  the  low  virulence  of  the  colon  bacillus,  it 
commonly  has  a  certain  amount  of  toxicity  and  it 
may  often  be  of  significance  even  as  an  agonal  in- 
fection. 

Postmortem  invasion  of  adjacent  structures,  as 
the  gall  bladder  and  liver  through  the  biliary  pas- 
sages, and  of  the  peritoneum  through  the  intesti- 
nal wall,  also  occurs. 
True  It  has  been  shown  that  the  colon  bacillus  occa- 
sionally causes  the  following  conditions :  Suppura- 
tive cholecystitis  which  may  extend  to  the  liver, 
peritonitis,  septicemia,  meningitis,  cystitis,  pyeli- 
tis and  ascending  suppurative  nephritis,  and  ab- 
scesses in  various  organs,  including  suppurative 
processes  in  the  middle  ear.  In  one  or  more  in- 
stances it  has  been  thought  that  it  caused  vegeta- 
tive endocarditis.  Probably  colon  infections  of  the 
gall  bladder  do  not  occur  in  the  absence  of  biliary 


Infections. 


COLON  BACILLUH.  303 

stasis.  Orflinarily  eases  of  peritonitis  in  wiiicli 
the  colon  bacillus  is  encountered  also  show  the 
presence  of  other  pathogenic  organisms,  as  strepto- 
cocci or  staphylococci;  this  is  always  the  case  in 
perforation  peritonitis.  Doubtless  wrong  conclu- 
sions have  been  drawn  in  many  instances  as  to  the 
bacteriology  of  peritonitis  from  the  fact  that  the 
colon  bacillus  readily  overgrows  many  other  bac- 
teria in  culture  media. 

Escherich  attributes  great  importance  to  this  or-  cystitis. 
ganism  as  the  cause  of  cystitis,  especially  in  chil- 
dren, and  states  that  it  is  probably  the  most  com- 
mon cause  of  cystitis,  pyelitis  and  ascending  sup- 
purative nephritis.  In  58  of  60  cases  of  cystitis  in 
children  the  colon  bacillus  was  found  either  alone 
or  in  mixed  cultures.  An  increased  agglutinating 
power  of  the  patient's  serum  for  the  organism  cul- 
tivated from  the  urine  is  noted  in  these  cases. 

Great  interest  attaches  to  the  colon  bacillus  in  Diarrheas, 
relation  to  enterocolitis  and  dysenteric  diseases. 
Escherich  speaks  of  an  enteritis  follicularis,  or 
colitis  contagiosa,  or  colicolitis,  epidemics  of  which 
have  been  noted  at  different  times.  A  number  of 
these  epidemics  occurred  before  the  identification 
of  the  dysentery  bacillus,  and  certain  of  them  ma}' 
have  been  true  dysenteric  infections.  Neverthe- 
less, dysentery  bacilli  are  not  found  in  all  cases  of 
enterocolitis,  and  the  probability  that  genuine 
cases  of  colon  enteritis  occur  can  not  as  yet  be  neg- 
lected. 

A  specific  colon  toxin  has  not  been  obtained. 

Immunization  with  the  colon  bacillus  causes  the 
formation  of  bactericidal  amboceptors  and  agglu- 
tinins. 

Xot  all  strains  of  the  colon  bacillus  are  identical 


304  IXFECTIO^'  AND  IMMUNITY. 

Aqgtutinaiion.  in  tlioir  aiXglutinoiieiiic  ivei'ptors.  A  serum  whirli 
agglutinates  one  colon  strain  does  not  necessarily 
agglutinate  all  strains.  The  reaction,  according  to 
Paltaul'  and  others,  is  largely  an  individual  one. 
The  serum  of  a  patient  with  a  colon  infection  will 
agglutinate  the  strain  causing  the  disease,  but  may 
not  ailect  other  strains.  Hence,  for  diagnostic 
purposes,  the  test  must  be  performed  with  the  cul- 
ture which  has  been  obtained  from  the  patient. 
Pfaundler  says  in  reference  to  colicolitis  that  if 
other  colon  infections  can  be  excluded,  and  if  the 
serum  of  the  patient  gives  the  agglutination  reac- 
tion in  a  dilution  of  1  to  50  with  the  bacillus 
which  has  been  cultivated  from  the  stools,  colon 
infection  is  indicated  (Paltauf). 

VI.    CHOLERA. 

In  1883  Koch  discovered  the  Vibrio  cholera  and 
cultivated  it  from  the  stools  of  cholera  patients. 
The  organism  may  be  cultivated  from  the  stools  of 
the  patients  invariably,  and  is  never  found  in  other 
diseases  nor  in  normal  stools,  except  in  the  case  of 
non-susceptible  persons  who  may  be  encountered 
during  an  epidemic.  The  latter  are  a  source  of 
danger  as  "cholera  carriers." 
Characteristics  Tvpicallv  the  cliolera  vibrio  is  about  1.5  microns 
oftheortian-  ^^^^  ^^^^  onc-fourth  as  broad.  The  cells  of  young 
cultures  have  the  so-called  comma  shape  which  has 
given  the  organism  the  name  of  the  comma  bacil- 
lus. The  form  in  reality  is  that  of  a  segment  of  a 
spiral.  AVhen  two  cells  are  attached  end  to  end  an 
S-shape  may  be  produced,  and  long  spirals  are 
made  up  of  many  cells  which  are  joined  at  the 
ends.  In  old  cultures  the  cells  may  assume  the 
form  of  thick  rods  or  even  appear  coccus-like.  Tlie 
vild'io  possesses  a  single  long  flngclluni.  Avliicli  is  sit- 


CHOLERA.  305 

iiatcd  at  the  end.  Altliongh  two,  four  and  six  fiag- 
ella  have  been  described,  KoUe  states  tliat  such  or- 
ganisms are  vibrios  of  another  nature.  In  the 
character  and  rapidity  of  their  movement,  as  seen 
in  a  hanging-drop,  Koch  compares  them  to  a 
swarm  of  mosquitoes.  Old  cultures  may  lose  their 
motility  to  a  large  extent.  The  cholera  vibrio 
does  not  form  spores,  although  certain  involution 
forms  simulate  them.  It  stains  readily  with  the 
ordinary  anilin  dyes  and  is  Gram  negative. 

The  comma  bacillus  grows  readily  in  alkaline  cultivation 
culture  media  with  characteristic  appearances ;  it  stools.  * 
is  an  obligate  aerobe  under  artificial  conditions,  in 
spite  of  the  fact  that  it  flourishes  in  the  intes- 
tines. The  optimum  temperature  lies  between  30° 
and  40°  C.  A  very  simple  method  of  obtaining  the 
organism  in  pure  culture  from  the  stools  was  dis- 
covered by  Koch.  In  tubes  of  peptone  bouillon 
which  have  been  inoculated  with  the  feces  of  a 
patient,  the  vibrio  proliferates  rapidly  and  within 
a  few  hours  exists  in  almost  pure  culture  at  the 
surface  of  the  liquid.  Isolated  colonies  are  ob- 
tained by  transferring  a  small  amount  of  the  sur- 
face fluid  to  tubes  of  liquefied  gelatin,  then  plating 
the  latter.  The  colonies  appear  in  a  few  hours  as  identification. 
small  translucent  points  from  which  pure  cultures 
are  made  on  a  suitable  medium.  For  more  positive 
identification  agglutination  tests  are  performed 
with  anticholera  serum.  The  Eoyal  Institute  for 
Infectious  Diseases  (Berlin)  keeps  on  hand  a  dried 
serum  of  known  strength  (1-10,000)  for  this  pur- 
pose. The  tests  being  made  with  high  dilutions, 
coagglutinins  for  other  vibrios  are  practically  elim- 
inated. To  the  agglutination  test  may  be  added 
the  "Pfeiffer  experiment,"  in  which  the  protective 


306  INFECTIOX    I  \ 7>  IMMUNITY. 

'  power  of  an  anticholera  serum  is  determined  wlien 
guinea-pigs  are  infected  intraperitoneally  with  the 
suspected  culture.  If  the  serum  shows  a  protective 
power  against  this  organism  which  approximates 
that  sliown  against  a  Icnown  cholera  vibrio,  or,  if 
the  organisms  are  dissolved,  the  diagnosis  of  chol- 
era is  justified.  In  performing  such  experiments 
the  serum  is  mixed  with  the  culture  before  injec- 
tion. 
Resistance.  The  resistance  of  the  cholera  vibrio  is  very  low. 
It  dies  in  about  two  hours  when  dried  (Koch)  and 
on  this  account  dust  infection  is  thought  not  to 
occur.  It  is  killed  instantly  by  the  boiling  tem- 
perature, and  in  five  minutes  at  80°  C.  It  is  ex- 
tremely susceptible  to  carbolic  acid  (killed  by  1 
per  cent,  in  five  minutes),  corrosive  sublimate  (1 
to  2,000,000  or  3,000,000  in  from  five  to  ten  min- 
utes), and  to  acids.  Calcium  chlorid  is  an  effi- 
cient disinfectant  when  thoroughly  mixed  with  the 
stools.  The  micro-organism  lives  in  distilled  water 
not  longer  than  twenty-four  hours,  in  ordinary 
water  for  several  days  to  several  weeks,  and  in  one 
instance  it  was  cultivated  from  the  water  of  an 
aquarium  after  several  months.  Its  life  is  short  in 
the  presence  of  putrefactive  bacteria  and  rapidly- 
growing  saprophytes,  dying  in  sewer  water  in  from 
twenty-four  to  thirty  hours  (Koch).  Because  of 
the  large  overgrowth  of  other  organisms,  the  vibrio 
can  rarely  be  cultivated  from  the  stools  later  than 
from  one  to  three  days  after  death.  Its  life  in  and 
on  foods  depends  on  the  reaction  (alkalinity  is 
favorable),  and  on  the  presence  or  absence  of 
moisture.  It  lives  longer  in  sterilized  milk  (ten 
days)  than  in  that  which  contains  other  micro-or- 
ganisms. 


CHOLERA.  307 

Infection  develops  in  the  small  intestines  fol-  infection 
lowing  ingestion  of  the  organisms.  Infection  by  Dissemination. 
way  of  the  lungs  or  through  wounds  does  not  take 
place.  In  the  patient  the  living  vibrio  occurs  only 
in  the  intestines^  and  it  is  excreted  only  with  the 
feces.  So  far  as  known^  it  has  no  normal  habitat 
outside  the  body,  although  a  stream  or  other  water 
supply  may  contain  the  vibrio  over  a  long  period 
through  constant  reinfection  of  the  water.  This 
can  only  occur,  directly  or  indirectly,  through  the 
stools  of  patients.  The  washing  of  soiled  linen  or 
bathing  in  water  which  is  used  for  drinking  and 
other  household  purposes  have  caused  outbreaks  of 
cholera.  The  water  supply  of  a  city  may  be  in- 
fected by  the  discharges  of  patients  who  are  con- 
fined to  a  ship.  Convalescents  may  retain  virulent 
organisms  in  their  stools  for  forty-eight  days 
(Kolle),  and,  as  stated,  healthy  persons  who  are 
insusceptible  to  cholera  and  who  have  resided  in 
an  infected  district  may  carry  virulent  vibrios  in 
their  intestines.  These  conditions  have  contrib- 
uted to  the  futility  which,  to  a  large  degree,  has 
met  attempts  to  limit  the  extension  of  cholera  by 
quarantine  measures.  Cholera  extends  from  coun- 
try to  country  along  the  lines  of  travel.  In  some 
instances  it  has  been  possible  to  trace  the  origin 
of  widespread  epidemics  to  the  delta  of  the  G-anges, 
a  region  in  which  the  disease  is  endemic.  Pilgrims 
from  India  carry  the  infection  to  Mecca,  and  pil- 
grims from  Eg3^pt  carry  it  to  their  native  land  on 
their  return  from  Mecca.  Either  from  Egypt,  or 
through  Arabia,  Asia  Minor  and  Southern  Eussia 
or  Turkey,  cholera  has,  with  more  or  less  rapidity, 
extended  to  Western  Europe.  The  development  of 
rapid  transit  has  increased  the  rapidity  with  which 


Epidemics. 


308  IXFECTION  AND  IMMUNITY. 

cholera  ma}-  extend.  From  Europe  the  disease  has 
been  carried  to  various  ports  of  the  western  conti- 
nent, Canada,  the  West  Indies  and  southern  ports 
of  the  United  States,  from  wliich  extension  has  oc- 
curred to  different  sections.  Of  six  widespread 
epidemics  of  the  past  one  hundred  years,  tliree 
liave  involved  thft  United  States,  reaching  consid- 
erable proportions.  The  means  of  introduction  is 
not  always  apparent. 

As  in  typhoid,  two  types  of  epidemics  arc  known, 
the  two  often  being  associated:  First,  that  caused 
by  water  infection,  and,  second,  that  in  which  the 
disease  spreads  by  direct  and  indirect  contact.  The 
explosive  character  of  an  epidemic  caused  by  in- 
fection of  a  water  supply  is  much  more  striking 
than  in  the  case  of  typhoid  fever.  In  large  cities 
hundreds,  or  thousands,  may  be  striken  within  a 
day.  The  brief  incubation  period,  from  twelve  to 
twent3'-four  hours,  contributes  to  the  acuteness  of 
the  outbreak.  The  distribution  of  a  "water- 
borne"  epidemic  corresponds  with  the  distribution 
of  the  infected  water.  A  remarkable  occurrence  il- 
lustrating this  point  was  noted  in  the  epidemic 
which  attacked  Hamburg  in  1892.  In  certain 
streets  in  which  the  residents  of  the  two  sides  ob- 
tained their  water  supply  from  different  sources, 
one  of  which  was  infected,  cholera  was  limited  to 
that  side  which  was  supplied  with  infected  water. 
Only  irregular  cases  due  to  contact  infection  oc- 
curred on  the  opposite  side  of  the  street. 

Epidemics  which  are  due  solely  to  contact  infec- 
tion develop  slowly  and  irregularly.  A  common 
incident  is  the  successive  involvement  of  the  mem- 
bers of  a  family,  whereas  others  in  the  immediate 
neighborhood    are   unaffected.      Water-borne   epi- 


CHOLHRA.  309 

demies  are  invariably  complicated  by  tbe  occur- 
rence of  contact  infection.  Tlie  methods  of  con- 
tact infection  are  not  different  from  those  men- 
tioned under  typhoid  fever.  Food  or  milk  which 
has  been  infected  by  contaminated  water  or  by 
other  means  may  cause  the  development  of  isolated 
groups  or  cases. 

Animals  do  not  contract  cholera  under  natural  Susceptibility 
conditions.  By  rendering  the  gastric  contents  of 
guinea-pigs  alkaline  and  introducing  cultures  into 
the  stomach  through  a  tube,  Koch  induced  a  chol- 
era-like process  from  which  the  animals  died  with- 
in from  twenty-four  to  thirty-six  hours ;  an  intra- 
peritoneal injection  of  opium,  to  quiet  peristalsis, 
seemed  to  be  necessary  for  the  success  of  the  ex- 
periment. Similar  results  were  obtained  in  very 
young  rabbits  by  feeding  cultures  to  them  (Issaeff 
and  Kolle,  Metchnikoff).  Guinea-pigs  withstand 
the  subcutaneous  inoculation  of  moderate  amounts, 
but  are  very  susceptible  to  intraperitoneal  inocula- 
tion. Intravenous  injections  are  exceedingly  toxic 
for  rabbits,  and  a  fatal  cholera-like  condition  with 
localization  of  the  organisms  in  the  intestines  and 
intestinal  mucosa  has  been  produced  in  this  way 
(Thomas). 

The  essential  poison  of  the  cholera  vibrio  is  in-  Endotoxin. 
tracellular,  and  becomes  free  only  after  solution  of 
the  bacterial  cells.  Cultures  which  are  killed  care- 
fully as  by  chloroform  vapor  (Pfeiffer)  are  highly 
toxic,  although  the  fluid  alone  is  non-toxic.  The 
filtrates  of  young  cultures  have  little  or  no  poison- 
ous action.  The  toxicity  of  older  filtrates  is  due 
partly  to  the  solution  of  the  bacteria  with  conse- 
quent liberation  of  endotoxin,  and  perhaps  also  to 
secondary   disintegration   products   which   have   a 


the  Intestines. 


310  IXFECTIOX  A\D  IMMUNITY. 

certain  toxicity.  Tlie  soluble  toxin  of  Metclini- 
koff,  Eoiix,  and  Taurclli-Salimbeui  is  a  dissolved 
endotoxin  and  not  a  secretion  of  the  living  cells, 
according  to  Kolle. 
Conditions  in  Kocli  considcrs  that  cholera  is  an  acute  infec- 
tious process  of  the  intestinal  epithelium,  whereas 
the  general  condition  is  one  of  acute  intoxication. 
It  is  assumed  that  the  condition  in  the  intestines 
corresponds  to  that  in  the  culture  media,  i.  e.,  that 
here,  too,  no  true  soluble  toxin,  comparable  with 
that  of  diphtheria  or  tetanus,  is  secreted,  but  that 
the  toxin  which  eventually  reaches  the  circulation 
is  that  which  is  liberated  from  the  bacteria  after 
the  latter  have  been  dissolved  by  the  bacteriolysin 
of  the  plasma,  or  perhaps  by  the  leucoc}i;es.  Doubt- 
less a  great  deal  of  endotoxin  is  liberated  in  the  in- 
testinal canal,  but  it  is  Koch's  conception  (cited 
by  Kolle)  that  the  primary  intoxication  comes 
from  those  organisms  which  have  penetrated  be- 
tween and  beneath  the  ei^ithelial  cells  and  here 
have  undergone  solution.  One  effect  of  the  toxin 
in  this  situation  is  to  cause  desquamation  of  the 
intestinal  epithelium,  as  a  consequence  of  which 
rapid  absorption  of  the  toxin  from  the  intestinal 
canal  takes  place  through  the  denuded  surface. 
This  theory  supposes  that  the  toxin  is  not  readily 
absorbed  through  the  intact  epithelium.  The  liv- 
ing vibrio  has  never  been  cultivated  from  the 
blood. 

The  changes  in  the  intestines  depend  on  the 
duration  of  the  infection.  In  cases  which  prove 
fatal  within  a  few  hours  the  mucosa  shows  only 
moderate  general  reddening,  which  is  intensified 
at  the  borders  of  Peyer's  patches  and  the  solitary 
follicles.     The  intestinal  contents  are  of  a  rather 


C  HOLE  It  A.  311 

clear  fluid  nature  in  which  are  suspended  flakes  of 
mucus  and  epithelium;  the  fluid  may  be  tinged 
with  blood.  With  a  longer  duration  the  destructive 
processes  in  the  mucosa  become  more  intense,  and 
consist  largely  of  desquamation  of  the  superficial 
epithelium  and  intense  congestion  of  the  denuded 
submucosa.  In  the  more  prolonged  cases,  "chol- 
era-typhoid," the  mucosa,  especially  above  the  ileo- 
cecal valve,  may  show  diphtheritic  necrosis.  The 
serous  surface  of  the  intestines  is  injected. 

The  rational  prophylaxis  founded  by  Koch,  on  Prophylaxis. 
a  knowledge  of  the  biologic  characteristics  of  the 
comma  bacillus,  has  proved  of  great  efficiency. 
The  essential  points  are  the  following:  1.  Imme- 
diate bacteriologic  examination  of  the  stools  in 
suspicious  cases.  2.  Absolute  isolation  of  patients, 
in  a  hospital  whenever  possible.  3.  Thorough  dis- 
infection of  the  stools,  linen,  room  and  all  articles 
with  which  the  patient  has  been  in  contact,  includ- 
ing water-closets  and  privies.  4.  Continued  iso- 
lation during  convalescence  until  the  stools  are 
free  from  vibrios.  5.  Eepeated  bacteriologic  ex- 
amination of  the  stools  of  those  who  have  been  in 
contact  with  cholera  patients  until  their  freedom 
from  vibrios  is  assured.  6.  Frequent  examination 
of  the  water  supply  at  different  points  in  order  to 
detect  the  occurrence  of  water  infection.  7.  In 
case  water  infection  exists,  exclusion  of  the  water 
from  all  domestic  uses,  and  the  institution  of 
means  to  rid  the  water  of  infection.  This  may  be 
done  in  the  case  of  infected  wells,  but  in  the  case 
of  large  systems  reconstruction  may  be  necessary 
for  future  protection.  Water  for  household  use 
should  be  boiled.  Kolle  compares  the  conditions 
in   Germany  and  Eussia  during  the  epidemic  of 


312  iXFKcrioy  A\n  iMMrxiiy. 

ISy.V^-i.  In  Gennaiiy,  where  Koeirs  prineiples  of 
prophylaxis  were  rigidly  observed,  about  10,000 
cases  occurred,  9.000  of  which  were  confined  to 
Hamburg,  whereas  in  Eussia,  where  precautions 
were  not  enforced  strictly  or  generally,  800,000 
cases  developed  during  the  same  period. 
Vaccination.  Protective  inoculation  has  shown  itself  to  be  of 
distinct  value  for  prophylaxis.  Ferran,  a  Span- 
iard, first  practiced  vaccination  on  a  large  scale  in 
1884,  although  little  definite  knowledge  of  the 
value  of  the  procedure  resulted  from  his  Avork. 
He  is  supposed  to  have  used  impure  cultures.  Hafi'- 
kine  introduced  protective  inoculation  on  a  large 
scale  in  India,  and  up  to  1895  had  inoculated  40,- 
000  persons.  Following  Pasteur's  method  with 
anthrax,  he  used  two  vaccines.  Vaccine  1  was  a 
culture  which  had  been  attenuated  by  prolonged 
growth  at  39°  C.  Vaccine  2,  which  was  adminis- 
tered five  days  later,  was  a  virulent  culture.  The 
living  organisms  were  used  in  both  vaccines  and 
the  injections  were  given  subcutaneously.  The 
local  and  general  symptoms  w^ere  mild.  Instead 
of  living  cultures  Kolle  has  proposed  the  use  of 
virulent  cultures  which  have  been  killed  by  expo- 
sure to  a  temperature  of  58°  C.  for  one  hour.  The 
vaccine  is  preserved  by  the  addition  of  0.5  per 
cent,  phenol.  In  the  Japanese  epidemic  of  1902 
this  method  was  used  on  an  extensive  scale.  The 
incidence  of  disease  among  the  uninoculated  was 
13  per  cent.,  among  the  inoculated  0.06  per  cent. ; 
the  mortality  among  the  uninoculated  was  10  per 
cent.,  among  the  inoculated  only  0.02  per  cent. 
The  disease,  when  it  occurred  in  the  inoculated, 
was  of  a  mild  type.  A  single  injection  of  from  2 
to  4  mg.  of  a  killed  agar  growth  was  given  sub- 


CIIOLJ'JJiA.  ■      313 

cutaneously  (cited  by  Kolle).  Strong  has  pro- 
posed the  use  of  the  products  of  autolysis  of  the 
cholera  vibrio  as  a  vaccinating  substance,  a  method 
founded  on  the  observations  of  Neisser  and  Shiga 
in  relation  to  typhoid,  and  of  Conradi  and  Drigal- 
ski  in  relation  to  dysentery.  The  local  and  general 
symptoms  are  said  to  be  of  a  mild  type.  The 
method  has  had  no  practical  trial. 

From  what  was  said  above  in  connection  with  ^^"(i^^l^^ 
the  so-called  cholera  carriers,  it  is  evident  that  not  susceptibility. 
all  are  equally  susceptible  to  infection  with  chol- 
era. In  the  few  instances  in  which  infection  has 
been  attempted  deliberately,  some  contracted  the  . 
disease,  at  least  one  case  ending  fatally,  whereas  in 
others  either  a  mild  infection  or  none  at  all  took 
place.  The  conditions  on  which  such  cases  of  in- 
dividual immunity  depend  are  not  known  conclu- 
sively, although  it  is  often  intimated  in  a  general 
way  that  a  strong  bactericidal  power  of  the  body 
fluids,  or  a  high  phagocytic  power  on  the  part  of 
leucocytes,  is  responsible  for  it.  The  gastric  juice, 
on  account  of  its  acidity,  offers  a  barrier  to  the 
passage  of  living  vibrios  into  the  small  intes- 
tines, and  this  is  particularly  true  of  cholera. 
It  is  nevertheless  evident  that  the  barrier  in  many 
instances  is  not  a  serious  one.  A  number  of  cases 
are  recorded  in  which  investigators  while  working 
with  cultures  have  become  infected  with  cholera, 
the  cases  running  typical  courses  which  sometimes 
ended  fatally  (Pfeiffer,  Pfuhl  and  others).  Or- 
ganisms which  are  ingested  with  water  may  pass 
rapidly  to  the  intestines  without  being  affected  by 
the  acid  of  the  stomach,  or  when  taken  with  food 
they  may  be  buried  in  the  latter  and  hence  not 
come   in  contact   with   tlie   gastric   secretion.     It 


314  INFECTIOy  AyO  IMMUyiTY. 

•  seems  probable  that  tlie  intestinal  epithelium  has 
a  certain  resistance  to  invasion  which  is  most  mani- 
fest in  the  case  of  those  who  do  not  become  in- 
fected in  spite  of  the  presence  of  the  organisms  in 
their  intestines.  Natural  immunity  appears  to  be 
one  which  is  directed  against  the  bacteria  rather 
than  against  the  endotoxin,  proliferation  of  the 
organisms  in  the  intestinal  epithelium  being  pre- 
vented. Poorly  nourished  individuals,  the  very 
young  and  the  very  old  are  particularly  suscepti- 
ble. Other  gastrointestinal  disorders,  in  the  pres- 
ence of  an  epidemic,  predispose  to  infection.  De- 
fects in  the  intestinal  epithelium,  or  a  decreased 
resistance  of  the  latter  ( ! ) ,  may  afford  favorable 
conditions  for  invasion. 
Acquired  Activc  immunity,  as  that  which  results  from  in- 
fection or  from  protective  inoculation,  is  charac- 
terized by  the  appearance  of  bactericidal  ambocep- 
tors, agglutinins  and  specific  ])recipitin8  in  the 
serum.  It  is  now  widely  believed  that  acquired  im- 
munity depends  on  the  presence  of  the  bactericidal 
amboceptors  in  the  circulation  and  body  fluids,  al- 
though Metchnikoff  holds,  on  the  other  hand,  that 
it  depends  largely  on  an  increased  phagocytic 
power  on  the  part  of  the  leucocytes.  According  to 
Pfeiffer  and  Marx,  the  antibodies  are  produced  in 
the  blood-forming  organs.  An  attack  of  cholera 
confers  immunity  of  prolonged  duration,  although 
it  is  not  always  absolute. 

Passive  immunity  is  readily  induced  in  animals 
by  the  injection  of  anticholera  serum.  As  in  other 
instances,  it  is  of  short  duration.  Doubtless  the 
same  condition  may 'be  induced  in  man.  Besredka 
has  proposed  mixed  active  and  passive  immuniza- 
tion   for   iiTotc-tivc  inoculation,   usinc"  kill('(l   bac- 


PLAGUE.  315 

teria  which  have  been  saturated  with  the  specific 
amboceptors. 

Serum  therapy  has  been  no  more  successful  in  serum 
cholera  than  in  typhoid  fever.  The  antitoxic  Agglutination. 
serum  of  Eoux  and  others  has  had  no  practical 
trial,  x^ccording  to  Achard  and  Bensaude,  the 
serum  of  cholera  patients,  on  the  third  or  fourth 
day  of  the  disease,  agglutinates  the  cholera  vibrio. 
However,  they  used  the  serum  in  dilutions  of  1-20, 
and  in  this  strength  even  normal  human  serum 
may  be  agglutinating  (PfeifEer  and  Kolle,  cited  by 
Paltauf).  Convalescents  even  after  seven  months 
may  show  an  agglutinating  power  of  from  1/100  to 
1/120. 

The  bacteriologic  examination  of  the  stools  is 
the  most  reliable  means  of  early  diagnosis  (see 
above). 

VII.    PLAGUE. 

Plague  was  known  in  the  second  and  third  cen- 
turies. In  the  sixth  century  it  ravaged  the  Eoman 
empire  and  destroyed  half  the  population  in  the 
eastern  provinces.  Under  the  name  of  the  'Tjlack 
death"  it  swept  over  Europe  in  1347-50  with  a 
sacrifice  of  one-fourth  of  the  inhabitants — about 
25,000,000.  During  the  fifteenth  and  sixteenth 
centuries  many  epidemics  prevailed  in  various 
parts  of  Europe,  and  the  disease  seemed  to  have 
fastened  itself  on  that  part  of  the  world.  However, 
the  pneumonic  form  of  the  disease,  the  most  con- 
tagious, gradually  became  less  common,  or  the  vir- 
ulence of  the  infection  diminished,  and  this, 'with 
the  institution  of  quarantine  regulations,  decreased 
the  prevalence  of  the  plague  during  and  following 
the  seventeenth  century.  ISTevertheless,  there  have 
been  occasional  outbreaks  in  Eastern  Europe  since 


31G  L\Fi:cT10.\  AM)  IMMUNITY. 

■  that  time.  Following  the  recrudescenee  of  plague 
iu  Hongkong  in  1893  and  in  other  places  later, 
the  disease  has  been  subjected  to  scientific  study, 
its  cause  has  been  discovered,  and  the  importance 
of  rigid  quarantine  measures  at  seaports  in  pre- 
venting its  universal  extension  has  been  proved. 
Characteristics  j^  ^j^g  Hongkong  epidemic  of  1893-4  Kitasato 
qanism.  -^i^^  Yersin,  working  independently,  discovered  the 
bacilhis  of  plague,  Bacillus  pestis.  The  organism  is 
minute  (1.5  to  1.75  by  0.5  to  0.7  microns),  and 
typically  is  of  long  oval  shape.  The  frequent  oc- 
currence of  short  oval  cells  (coccus  form),  longer 
rods  and  distorted,  swollen,  vacuole-like  cells  (in- 
volution or  degeneration  forms)  signifies  a  liigli 
degree  of  pleomorphism  which  is  characteristic. 
The  longer  the  disease  has  lasted,  or,  on  the  other 
hand,  the  older  the  culture,  the  more  numerous  are 
the  atypical  forms.  In  bouillon  long  chains  de- 
velop. It  is  non-motile,  has  no  flagella  aiid  forms 
no  spores.  A  capsule  may  be  demonstrated  by  ap- 
propriate technic.  It  does  not  stain  by  Gram's 
method,  and  with  methylene  blue,  carbol  fuchsin, 
etc.,  the  ends  stain  more  densely  than  the  central 
portion  (polar  staining).  Because  of  its  general 
•  properties  it  is  placed  in  a  group  with  a  number  of 
bacteria  which  cause  hemorrhagic  septicemias  in 
various  animals — the  "hemorrhagic  septicemia 
group." 

There  occurs  in  bouillon  the  so-called  "stalac- 
tite" growth,  in  which  visible  processes  extend 
from  the  surface  toward  the  bottom,  where  they 
meet  other  processes  which  extend  toAvard  the  sur- 
face ("stalagmites").  These  formations  utilize  as 
their  starting  points  the  side  of  the  fla>k  or  dro])S  of 
butter  or  oil  which  are  placed  on  the  surface.  Cer- 


PLAGUE.  317 

tain  other  organisms  grow  in  a  similar  manner. 
It  is  said  to  be  a  characteristic  feature  of  the 
plague  bacilli  that  many  involution  forms  appear 
on  agar  which  contains  3  per  cent,  of  sodium 
chlorid.  The  optimum  temperature  for  growth  is 
from  25°  to  30°  C,  which  is  somewhat  lower  than 
that  for  most  pathogenic  organisms.  It  grows 
rather  slowly  even  under  the  best  conditions.  In 
mixed  cultures  it  is  overgrown  by  saprophytic  or- 
ganisms (e.  g.,  colon  bacillus). 

The  plaffue  bacillus  may  live  for  from  four  to  viability  and 
seven  days  in  the  putrefying  organs  of  man  or  ani- 
mals. Its  virulence  may  be  retained  in  the  cadaver 
of  a  rat  for  two  months  (Bandi  and  Stagnitta- 
Balistreri).  During  this  time  the  organisms  pene- 
trate all  the  tissues  of  the  body,  even  growing 
through  the  skin.  It  may  live  in  the  pus  of  a 
bubo  for  twenty  days  when  unmixed  with  other 
organisms  (Albrecht  and  Gohn)  ;  in  the  sputum 
from  plague  pneumonia  for  ten  days;  in  various 
foods,  as  milk,  potatoes,  for  one  to  three  weeks;  in 
water  from  five  to  twenty  days,  depending  on  the 
number  of  saprophytes  which  are  present;  in  earth 
from  two  weeks  to  three  months,  depending  on  the 
quantity  of  organic  matter  and  other  organisms. 
In  all  these  instances  the  higher  the  temperature, 
i.  e.,  above  30°  C,  and  the  more  numerous  the 
saprophytic  organisms,  the  shorter  is  the  life  of  • 
the  plague  bacillus.  In  winter,  when  contaminat- 
ing saprophytes  grow  less  rapidly,  the  plague  bacil- 
lus lives  longer.  Its  resistance  to  desiccation,  sun- 
light and  disinfecting  agents  is  rather  low,  par- 
ticularly when  the  surrounding  temperature  is 
above  30°  C.  In  temperatures  of  from  29°  to  31° 
C,  when  thoroughly  dried,  it  rarely  lives  longer 


3 IS  I.XFECTIOy  AM)  IMMUNITY. 

than  from  six  to  seven  days,  whereas  at  lower  tem- 
peratures, 16°  to  20°  C,  cultures  may  he  ohtained 
after  from  one  to  several  weeks,  depending  on  the 
material  which  contains  the  organisms.  It  lives 
longer  in  woolen  and  cotton  threads  (clothing) 
than  when  isolated  as  in  dust;  hence,  dust  infection 
is  improhahle  (Dieudonne).  In  sputum  (plague 
pneumonia)  and  purulent  exudates  in  which  the 
hacilli  become  incrusted  to  a  degree,  life  may  per- 
sist for  from  three  to  four  weeks.  Sunlight  kills 
tliem  in  from  two  to  six  hours,  depending  on  the 
temperature  and  the  proximity  of  the  organisms  to 
the  surface.  Although  cultures  for  the  purpose  of 
vaccination  have  been  killed  at  a  temperature  of 
G5°  C.  for  one  hour,  precautions  to  insure  an  even 
distribution  of  the  heat  are  necessary  to  render  cer- 
tain the  death  of  all  organisms.  A  temperature  of 
100°  C.  kills  them  at  once,  and  80°  C.  in  from  five 
to  ten  minutes  (moist  heat) .  They  are  very  resis- 
tant to  cold,  remaining  alive  at  a  temperature  of 
— 20°  C.  for  several  weeks,  even  when  repeatedly 
thawed  out  during  this  time,  and  they  even  prolif- 
erate slowly  at  from  4°  to  7°  C. 
virulence  Cultures  of  the  plague  bacillus  retain  their  viru- 
lence over  a  long  period  when  kept  in  a  cool  dark 
place  and  wdien  not  allowed  to  dry.  However, 
they  often  loose  in  virulence  unaccountably.  The 
nature  of  the  toxic  substance  is  as  yet  obscure.  A 
concentrated  soluble  toxin  has  never  been  obtained 
in  cultures.  Filtrates  of  young  cultures  show  lit- 
tle or  no  toxicity,  whereas  in  older  cultures  the 
fluid  becomes  more  or  less  toxic  (liberation  of  en- 
dotoxin?). Lustig  and  Galeotti  extract  cultures 
with  0.75  to  1  per  cent,  potassium  hydroxid,  from 
which  they  precipitate  a  toxic  substance  with  ace- 


and  Toxins. 


PLAGUE.  319 

tic  or  hydrochloric  acid.  Markl  found  the  cell 
bodies  to  be  very  toxic  after  eight  weeks'  growth  at 
room  temperature,  provided  the  organisms  were 
killed  by  chloroform  rather  than  by  heat;  killing 
by  heat  destroys  the  toxic  substance  largely.  He 
believes  some  metabolic  product  of  the  organism 
is  the  chief  toxic  constituent,  claiming  at  the  same 
time  the  presence  of  a  certain  amount  of  soluble 
toxin. 

The  plague  bacillus  is  exceedingly  virulent  for  virulence 
rats,  guinea-pigs  and  monkeys;  somewhat  less  f*"" ^""''ais. 
virulent  for  mice  and  adult  rabbits ;  other  animals, 
cats,  dogs,  swine,  cows,  horses,  sheep,  goats,  may  be 
infected  artificially,  although  they  commonly  re- 
cover even  after  large  doses.  Eats  and  guinea- 
pigs  may  be  infected  by  subcutaneous,  intraperito- 
neal and  intravascular  injections,  by  the  feeding  of 
infected  material  or  by  placing  it  on  the  nasal  mu- 
cous membrane  or  in  the  conjunctival  sac,  and  by 
inhalation  experiments,  the  last  method  commonly 
resulting  in  plague  pneumonia.  Guinea-pigs  and 
young  rabbits  die  of  plague  septicemia  in  from 
four  to  five  days  when  cultures  or  material  con- 
taining the  organisms  (sputum,  feces,  organs  from 
plague  cases),  are  rubbed  into  the  shaven  or  even 
unshaven  skin  (Albrecht  and  Gohn).  This  experi- 
ment is  of  value  for  detecting  virulent  plague  ba- 
cilli and  separating  them  from  contaminating  or- 
ganisms. Following  inoculation  into  a  cutaneous 
or  mucous  s^irface  a  local  reaction  of  varying  in- 
tensity develops  in  which  the  subcutaneous  tissue 
becomes  edematous  or  even  hemorrhagic,  in  a  num- 
ber of  hours  the  regional  lymph  glands  become 
swollen  and  hemorrhagic,  and  in  from  two  to  five 
days  the  animals  die  of  plague  septicemia.     Cul- 


320  lyPECTIOy  AND  IMMUNITY. 

,  tures  of  low  virulence  not  infrequently  cause  a 
chronic  infection  which  is  characterized  by  the  for- 
mation of  large  granulomatous  nodules  on  the  sur- 
face of  the  liver  and  spleen  and  in  the  omentum. 
Such  foci  contain  many  plague  bacilli,  and  the 
death  of  the  animal  results  in  a  few  weeks  from 
intoxication  or  from  general  infection.  Although 
rabbits  are  much  less  susceptible  than  rats  or 
guinea-pigs,  young  animals  succumb  to  cutaneous 
inoculation. 
Endemic       Dicudonne  cites  four  foci  in  which  plague  is 

Plague.  .       ^  . 

known  to  be  endemic  at  the  present  time :  One  is 
in  China  (province  of  Yiinnan),  from  which  the 
Hongkong  epidemic  originated;  a  second  in  the 
Himalayas,  which  led  to  the  outbreak  in  Bombay; 
a  third  in  a  mountainous  region  south  of  Mecca, 
and  a  fourth  was  found  by  Koch  and  Zupitza  in 
British  East  Africa  near  the  source  of  the  White 

Plague  The  opinion  is  held  by  many  that  plague  is  pri- 
marily a  disease  of  the  rat  and  that  certain  regions 
remain  pest-infected  because  of  this  fact.  Eats,  in 
certain  districts,  suffer  from  a  chronic  form  of  the 
disease,  and  it  is  possible  that  the  organism  at 
times  acquires  increased  virulence,  as  a  conse- 
quence of  which  the  infection  becomes  widespread 
and  rapidly  fatal  among  these  animals.  It  is  prob- 
able that  the  chief  method  of  transmission  from 
rat  to  rat  is  through  the  eating  of  plague  cadavers. 
The  possibility  of  transmission  from  one  animal 
to  another  by  means  of  fleas  is  upheld  by  some. 
The  blood  which  fleas  suck  from  infected  rats  fre- 
quently contains  bacilli,  but  transmission  to  other 
rats  by  the  bites  of  fleas  is  still  disputed. 

The  means  by  w^hich  the  disease  extends  from 


in  Rats. 


PLAGUE.  321 

rat  to  man  are  not  definitely  determined.  This 
much  is  known,  however:  First,  that  the  bacilli 
are  excreted  in  the  urine  and  feces  of  infected  ani- 
mals, and,  second,  that  the  disease  attacks  those  Houses. 
especially  who  live  in  dark,  damp,  filthy  quarters 
in  which  rats  are  numerous.  Europeans  who  live 
under  hygenic  conditions  in  plague-infected  dis- 
tricts rarely  contract  the  disease.  A  great  mor- 
tality among  the  rats  not  uncommonly  precedes  an 
outbreak  of  plague  in  man.  The  existence  of 
"plague  houses"  may  depend  on  the  prevalence  of 
the  disease  among  the  rats  which  infest  the  houses. 
On  the  other  hand,  the  organisms  excreted  by  a 
plague  patient  through  the  sputum,  urine  or  feces, 
find,  in  the  conditions  described  above,  surround- 
ings which  favor  their  prolonged  life;  hence,  the 
occurrence  of  subsequent  infection  in  the  same 
house  in  many  instances  may  be  traceable  to  a  pre- 
vious case. 

The  theory  has  been  advanced  also  that  fleas  Ffeas. 
may  be  an  important  means  of  transferring  plague 
from  rats  to  man.  This  is  objected  to  on  the 
ground  that  every  animal  has  its  peculiar  flea  and 
that  the  flea  of  the  rat  will  not  bite  man.  Never- 
theless, it  may  alight  on  the  skin  of  man  tem- 
porarily and  there  discharge  bacillus-laden  excre- 
tions. Flies,  in  a  like  manner,  may  distribute  the 
bacilli  from  rats  or  the  infected  excretions  of  man. 

When  plague  invades  a  new  country  it  commonly 
makes  its  first  appearance  in  coast  cities.  Pre-  - 
sumably  this  is  accomplished  through  infected  rats 
which  may  board  a  ship  during  its  stay  in  a  pest- 
ridden  harbor,  and  which  subsequently  escape  at 
the  new  port. 

Epidemics  of  plague  lack  the  explosive-like  sud- 


322 


IXFECTIOy  AXD  IMMUNITY. 


Epidemics. 


Infection 
Atria. 


donncss  in  their  development  which  characterizes 
cliolera  and,  to  a  certain  extent,  typlioid  and  dys- 
entery. The  cases  occur  in  <j:roups  and  in  particn- 
hir  houses  in  such  a  manner  that  direct  and  indi- 
rect contact  seem  to  be  hirgely  responsible  for 
transmission.  Every  epidemic  of  plague  may  be 
divided  into  three  stages :  a  slow  progression  from 
small  centers,  an  acme  of  widespread  death,  and  a 
slow  recession  (Dieudonne).  It  seems  probable 
that  the  disease  spreads  rapidly  and  extensively 
only  wlien  the  pneumonic  form  prevails. 

In  man  infection  takes  place  tlirough  the  skin 
most  frequently,  although  the  mucous  membranes 
of  the  mouth,  nose,  pharynx,  tonsils  or  the  con- 
junctiva are  possible  infection  atria.  Often  no 
local  reaction  is  produced,  and  the  point  of  en- 
trance may  be  indicated  only  in  a  general  way  by 
the  swollen  lymph  glands  of  the  region.  Infre- 
quently a  pustule  or  small  carbuncle  marks  the 
point  of  entrance.  Primary  plague  pneumonia  is 
caused  by  the  inhalation  of  pest-laden  material, 
particularly  fine  particles  of  sputum  from  a  pneu- 
monic case,  and  perhaps  also  by  the  inhalation  of 
infected  dust ;  the  latter  is  probal)ly  of  less  impor- 
tance because  of  the  short  life  of  the  organism  in 
dust.  Even  in  ordinary  speaking  minute  drops  of 
saliva  are  thrown  into  the  air.  Infection  is  thought 
not  to  occur  through  the  stomach  or  intestines. 
In  the  pneumonic  and  septicemic  forms,  the  in- 
fected urine  and  feces  contribute  to  the  dissemina- 
tion of  the  organisms.  Transmission  by  indirect 
contact,  as  Ijy  infected  clothing  and  linen,  has  been 
noted  in  many  instances.  Compared  with  pneu- 
monic and  septicemic  plague  the  bul)onie  form  is 
much  less  dangerous  to  a  communitv. 


PLAQUE.  323 

Following  cutaneous  infection  the  regional 
lymph  glands  become  swollen  and  hemorrliagic, 
and  undergo  more  or  less  extensive  necrosis.  When 
the  infection  extends  beyond  the  lymph  glands  the 
blood  may  contain  enormous  quantities  of  bacilli 
(plague  septicemia),  and  the  same  condition  fol- 
lows plague  pneumonia ;  in  the  event  of  general  in- 
fection death  follows  in  a  few  hours.  "Secondary 
pneumonia"  and  also  "secondary  buboes"  develop 
as  a  consequence  of  blood  infection.  Hemorrhages 
into  the  mucous  membrane  (especially  the  stom- 
ach or  cecum),  endothelial  surfaces  (pericardium), 
and  various  parenchymatous  organs,  with  extreme 
degeneration  of  the  latter  (liver,  kidneys  and 
heart),  are  characteristic  anatomic  changes.  The 
spleen  is  usually  swollen.  The  toxic  substance 
evidently  has  affinities  for  many  tissues. 

Mixed  infection  with  the  streptococcus  is  not 
uncommon  and  is  a  serious  complication. 

The  following  are  important  points  for  prophy-  prophylaxis. 
laxis:  1.  Early  diagnosis  as  established  by  bac- 
teriologic  examination  of  blood,  sputum,  and  fluid 
taken  from  a  bubo  either  by  a  syringe  or  after  in- 
cision ;  2,  in  the  thorough  isolation  of  patients  and 
of  those  whose  have  been  exposed  to  infection;  3, 
in  the  disinfection  of  excretions,  of  clothing  and  of 
infected  houses,  which  in  some  instances  may 
mean  the  destruction  of  the  latter;  4,  in  the  de- 
struction of  rats;  5,  prophylactic  injections.  Up 
to  the  present  time  the  most  effective  measure  of 
getting  rid  of  rats  is  to  offer  a  bounty  for  each 
animal  caught,  as  practiced  in  Manila. 

The  vaccine  of  Haffkine  has  been  used  exten-  vaccines 
sively  in  India.     The  Indian  plague  commission 
found  that  the  incidence  of  disease  and  the  mor- 


324  INFECTION  AND  IMMUNITY. 

tality  were  lower  among  tlie  inoculated  than  the 
uninoculated,  although  many  of  the  inoculated 
contracted  the  disease  in  a  benign  form.  The  vac- 
cine consists  of  bouillon  cultures  which  have  grown 
for  six  weeks  with  stalactite  formation  (see  above), 
then  killed  by  exposure  to  a  temperature  of  65°  C. 
for  one  hour;  from  0.5  to  3.5  c.c.  are  injected,  ac- 
cording to  the  age  and  size  of  the  individual.  One 
or  more  subsequent  injections  may  be  given.  The 
local  and  general  reactions  are  of  moderate  sever- 
ity. Protection  becomes  manifest  only  several 
days  after  the  inoculation  and  may  persist  for 
many  weeks  or  months.  The  vaccine  recommended 
by  the  German  commission  consists  of  two  days' 
old  agar  cultures  which  have  been  killed  by  heat 
(65°  C.  for  one  hour).  Lustig  and  Galeotti  utilize 
the  toxic  precipitate  described  above  as  a  vaccine. 
Terni  and  Bandi  inoculate  rabbits  or  guinea-pigs 
intraperitoneally  with  the  plague  bacillus  and 
after  or  just  preceding  death  collect  the  peritoneal 
exudate,  in  which  the  organisms  are  allowed  to  pro- 
liferate still  further  for  twelve  hours.  The  bacilli 
are  then  killed  at  a  low  temperature,  and  this 
fluid,  after  an  addition  of  a  preservative,  consti- 
tutes their  vaccine.  Although  the  last  three  vac- 
cines have  proved -of  value  in  animal  experiments, 
they  have  not  as  yet  been  used  extensively  in  man. 

Besredka,  also  Shiga,  recommend  the  use  of 
mixed  active  and  passive  immunization,  as  sug- 
gested in  relation  to  typhoid  and  cholera,  in  this  in- 
stance naturally  using  plague  bacilli  (killed)  and 
anti-plague  serum.  Shiga  reported  good  results 
by  the  use  of  the  combined  method  in  the  epidemic 
in  Kobe. 

The  immunity  which  is  produced  by  protective 


PLAQUE.  325 

inoculation,  like  that  which  follows  natural  infec-  immunity. 
tion,  is  considered  to  be  antibacterial  inasmuch  as 
the  serum  acquires  increased  bactericidal  power  for 
the  bacillus,  but  shows  no  ability  to  neutralize  its 
toxic  constituents.  As  in  relation  to  many  other 
infections,  however,  we  are  not  in  position  to  ig- 
nore the  possibility  of  an  increased  phagocytic 
power  on  the  part  of  the  leucocytes.  The  influence 
of  opsonins  is  essential  for  experimental  phago- 
cytosis. Wright  characterizes  the  plague  bacillus 
as  "an  organism  which  is  absolutely  insensible  to 
the  bactericidal  action  of  the  normal  human  blood 
fluids,  but  eminently  sensible  to  the  opsonic  action 
of  these  fluids."  The  immunity  which  follows  in- 
fection is  of  long  duration. 

Prophylactic  injections  of  antiplague  serum  pro-  serumtherapy 
duce  a  temporary  immunity  of  about  two  weeks'  faxis.*^*"*  '^ 
duration.  The  Pasteur  Institute  prepares  the 
serum  of  Yersin  by  immunizing  horses  first  with 
killed  and  then  with  living  cultures.  The  immun- 
ization is  difficult  and  from  several  months  to  a 
year  and  a  half  are  required  for  the  production  of 
a  strong  serum.  Wlien  the  blood  is  drawn  eventu- 
ally its  freedom  from  living  plague  bacilli  and 
from  toxic  substances  must  be  assured.  The  im- 
munizing value  of  the  serum  is  determined  by  that 
quantity  which  will  save  a  mouse  from  a  fatal  dose 
of  living  plague  bacilli,  the  serum  being  given 
twenty- four  hours  in  advance  of  the  culture.  This 
is  accomplished  by  0.1  to  0.02  c.c,  depending  on 
the  strength  of  the  serum.  Its  curative  power  is 
estimated  from  that  quantity,  0.5  to  0.1  c.c, 
which  saves  a  mouse  when  administered  sixteen 
hours  after  the  injection  of  an  otherwise  fatal  dose 
of  culture.     For  protective   inoculation   in   man 


326  l.\FEtTlO.\    A\D  IMili MTY. 

,  from  10  to  20  e.c.  are  rocoinmended,  and  for  cura- 
tive purposes  from  30  to  50  e.c.  Concerning  the 
value  of  this  serum  Dieudonne  concludes  as  fol- 
lows: "On  tlie  basis  of  the  results  obtained  in 
man  and  in  animal  experiments  we  can  attribute 
no  positive  curative  value  to  the  Parisian  serum, 
although  a  certain  influence  on  the  course  of  the 
disease  can  not  be  denied.  On  the  other  hand,  the 
serum  is  suitable  for  protective  inoculation  when 
immediate  immunit}-  is  necessary,  as  for  those  who 
are  caring  foV  cases  of  plague  pneumonia.  Since, 
however,  the  protection  afforded  by  this  means  per- 
sists only  for  a  few  days,  subsequent  active  immun- 
ization with  killed  cultures  is  indicated  as  soon  as 
possible  for  those  persons  who  are  exposed  to  in- 
fection for  some  time."  The  favorable  results 
noted  by  a  number  of  observers  would  seem  to  jus- 
tify further  use  of  the  serum  for  curative  pur- 
poses. 

The  serum  of  Tavel,  prepared  at  the  Institute 
of  Bern,  is,  like  that  of  Yersin,  bactericidal  and 
agglutinating.  Antitoxic  as  well  as  bactericidal 
properties  are  claimed  for  the  serum  of  Lustig, 
which  is  prepared  by  immunization  with  the  toxic 
precipitate  mentioned  above.  It  has  been  used  ex- 
tensively in  the  treatment  of  plague  and  in  a  num- 
ber of  small  epidemics  favorable  though  not  thor- 
oughly convincing  results  were  reported.  The 
serum  of  Markl,  which  is  supposed  to  be  antitoxic, 
has  had  no  j^ractical  trial.  It  is  prepared  by  im- 
munization with  old  cultures  which  have  been 
killed  by  chloroform. 
Aogiutination.  Although  the  serum  of  patients  acquires  a  cer- 
tain agglutinating  power,  it  is  rather  low  (1/3  or 
1/5),  and  does  not  become  manifest  until  during 


ANTHRAX.  327 

the  second  week  of  the  disease.  Before  this  time 
diagnosis  by  clinical  or  bacteriologic  means  can  be 
made  with  certainty;  hence,  for  clinical  diagnosis 
the  reaction  has  little  value.  On  the  other  hand, 
a  strong  artificial  agglutinating  serum  obtained 
by  the  specific  immunization  of  animals  is  of  great 
value  for  the  identification  of  the  plague  bacillus 
when  cultures  have  been  obtained  from  suspected 
cases.  Artificial  serums  may  agglutinate  in  dilu- 
tions of  from  1/1000  to  1/6000. 

B.  Serum  in  acquired  immunity  is  not  bacteri- 
cidal, or  knowledge  on  this  point  is  deficient. 

I.    ANTHRAX. 

From  the  standpoint  of  infection  and  immunity 
anthrax  is  of  particular  interest.  It  is  the  first 
disease  of  which  the  bacterial  etiology  was  proved 
and  in  which  the  specific  microbe  was  used  in  pure 
culture  for  the  production  of  artificial  immunity 
(vaccination). 

Anthrax  is  particularly  a  disease  of  cattle  and 
sheep,  and  it  prevails  in  certain  European  coim- 
tries,  especially  Eussia,  in  Australia  and  in  South 
America.  It  does  not  occur  extensively  in  this 
country.  Definite  regions  are  at  times  heavily  in- 
fected, and  it  is  in  such  localities  that  the  disease 
is  most  frequently  transmitted  to  man. 

As  early  as  1850  Rayer  and  Devalue,  also  Pol-  Baciirus_ 
lender,  had  discovered  the  presence  of  small  rods 
and  filaments  in  the  blood  of  animals  which  had 
died  of  anthrax,  and  the  work  of  Koch,  Pasteur 
and  others  soon  established  that  this  rod,  the  anth- 
rax bacillus,  is  the  cause  of  anthrax.  The  discov- 
ery of  Koch  that  the  bacillus  forms  extremely  re- 


328 


INFECTION    AND    IMMUNITY. 


Spores. 


Resistance 
and  Virulence. 


sistant  spores,  explained  the  persistence  with  which 
the  disease  infects  particuhir  localities. 

The  anthrax  hacilhis  is  a  fairly  large  organism, 
is  rod-shaped,  non-motile  and  grows  with  charac- 
teristic appearances  on  various  culture  media. 
With  the  proper  temperature  and  culture  medium, 
and  in  the  presence  of  free  oxygen,  the  formation 
of  spores  hegins  after  about  twenty-four  hours  of 
growth.  Their  evolution  is  complete  in  from  one 
to  two  days,  and  eventually  the  protoplasm  of  the 
cells  disintegrates  and  the  spores  are  set  free. 
Spores  are  not  formed  in  the  body  of  an  infected 
animal.  Spore  formation  is  not  essential,  how- 
ever, for  the  continued  life  of  the  organism;  at 
high  temperatures  (42°  C),  and  in  the  presence 
of  minute  amounts  of  acids  and  alkalis  or  of  car- 
bolic acid,  strains  may  be  so  altered  that  they  lose 
permanently  the  ability  to  produce  spores.  Under 
favorable  conditions  the  spores  germinate  com- 
pletely in  from  three-quarters  to  one  and  one-half 
hours  (Grethe)  by  a  process  in  which  they  lose 
their  refractive  appearance  and  assume  first  an 
oval  and  then  a  rod  shape.  In  the  body  a  capsule 
surrounds  the  bacillus,  and  it  grows  singly  or  in 
very  short  chains ;  in  culture  media  it  is  very  diffi- 
cult to  obtain  capsules.  The  long  threads  which 
appear  in  culture  media,  especially  bouillon,  are 
not  found  in  infected  animals. 

The  bacillus  itself  shows  no  unusual  resistance, 
l)ut  its  spores  are  more  resistant  than  those  of  any 
other  pathogenic  bacterium.  When  dried  on  a 
thread  they  have  been  known  to  live  for  from  ten 
to  twelve  years.  Corrosive  sul)limate  (1-2000) 
kills  them  in  forty  minutes  (Fraenkel),  and  direct 
sunlight  in  about  100  hours  (Moment).    Bacillus 


ANTHRAX.  329 

pybcyaneus,  streptococci,  staphylococci  and  the  ba- 
cillus of  Friedlander  are  said  to  antagonize  its 
growth,  and  Eettger  found  that  the  dried  B.  prodi- 
giosus  decreased  the  virulence  of  the  organism  for 
animals  when  the  two  were  injected. 

The  anthrax  bacillus  is  remarkable  for  its  infec- 
tiousness. A  twenty-millionth  of  a  loop  of  a  viru- 
lent culture  will  cause  a  fatal  infection  in  mice, 
guinea-pigs  and  rabbits,  when  given  subcutaneous- 
ly.  A  systemic  infection  may  be  produced  by  feed- 
ing the  spores  or  causing  animals  to  inhale  them. 
The  gastric  juice  is  able  to  kill  the  bacilli,  but  not 
the  spores,  which  germinate  after  they  reach  the 
intestines. 

The  organism  is  distributed  by  the  excretions 
of  diseased  animals,  and  after  their  death  the  ad- 
jacent soil  becomes  heavily  infected  by  the  dis- 
charges which  escape  from  the  intestines  and  blad- 
der. In  this  situation  the  bacilli  pass  into  the 
sporing  stage,  in  which  they  remain  viable  and 
virulent  for  a  long  time. 

The  infection  of  herds  usually  is  accomplished  infection 
by  the  ingestion  of  spores  which  have  been  distrib- 
uted in  this  way,  the  spores  germinating,  as  de- 
scribed above,  after  they  have  reached  the  intes- 
tines. The  disease  may  be  primary  in  the  skin  in 
the  form  of  malignant  pustule.  In  man  malignant 
pustule  is  the  commonest  type  of  infection,  occur- 
ring especially  among  those  who  have  to  do  with 
cattle  and  sheep.  The  bacilli,  however,  jnay  gain 
entrance  through  the  lungs  as  in  the  so-called 
"wool-sorter's''  disease,  which  is  caused  by  the  in- 
halation of  infected  dust  from  the  raw  material. 

The  generalized  infection  in  all  animals  is  rapid- 
ly fatal  (one  to  three  days),  and  the  occurrence  of 


330  IXFECTIOX    AND    IMMUNITY. 

doatli  is  sometinios  so  siuklon  as  to  be  called  apo- 
plectiform ;  in  man  the  mortality  is  about  50  per 
cent.  Malignant  pustule  runs  a  more  favorable 
course. 
To<iin.  The  general  infections  are  marked  by  symptoms 
of  intense  intoxication  and  acute  degenerative 
changes  are  produced  in  the  parenchymatous  or- 
gans. Massive  numbers  of  the  bacilli  are  found  in 
the  blood.  Xeither  a  soluble  toxin  nor  an  endo- 
toxin characteristic  for  the  organism  has  been  dem- 
onstrated up  to  the  present  time  (Sobernheim), 
although  there  is  abundant  clinical  and  anatomic 
evidence  of  intense  intoxication.  The  production 
of  mechanical  injuries  by  the  large  masses  of  ba- 
cilli in  the  circulation  is  doubtful. 
Prophylaxis  Rational  prophylaxis  involves  the  proper  dispo- 
sal of  the  bodies  of  animals  which  have  died  of 
anthrax,  the  exclusion  of  animals  from  fields 
known  to  be  infected,  suitable  disinfection  of  stalls, 
and  finally  protective  inoculation  against  the  dis- 
ease. Xo  part  of  the  anthrax  cadaver  should  be 
used  for  commercial  purposes,  because  of  the  dan- 
ger of  infecting  those  Avho  Avork  with  the  raw  ma- 
terials. Cleanliness  and  the  usual  precautions 
against  contagious  diseases  should  be  observed  by 
those  who  are  exposed  to  infection,  bearing  in  mind 
that  the  disease  may  be  transmitted  by  way  of  the 
lungs  and  alimentary  tract,  as  well  as  by  the  skin. 
Natural       It  is  probable  that  no  disease  is  more  perplexing 

Immunity  and     «  xi  j.        i       •     j.       j?    •  -j.       xi  ±i 

Susceptibility,  irom  thg  standpoint  of  immunity  than  anthrax. 
The  variations  in  susceptibility  and  immunity 
among  different  animals  are  extreme:  Guinea- 
pigs,  rabbits  and  mice  are  probably  more  suscepti- 
ble than  sheep  and  cattle ;  compared  with  these  the 
dog  and  rat  arc  relatively  immune,  whereas  fowls 


ANTHRAX.  331 

and  cold-blooded  animals  can  be  infected  with  dif- 
ficulty. Although  the  niicrolje  is  readily  killed  by 
suitable  serums  (rabbit,  e.  g.),  such  an  effect  is  not 
an  index  of  immunity.  The  serum  of  the  highly 
susceptible  rabbit  is  strongly  bactericidal  in  test- 
glass  experiments,  whereas  that  of  the  more  resist- 
ant dog,  or  rat,  has  little  or  no  bactericidal  power. 
Because  of  this  inconsistent  relationship  of  the 
serum  to  immunity,  and  since  the  leucocytes  have 
a  high  phagocytic  power  for  the  anthrax  bacillus, 
Ptruschky,  Frank  and  others  agree  with  Metchni- 
koff  in  assigning  variations  in  the  natural  immun- 
ity of  different  animals  to  variations  in  phago- 
cytic power.  Bail  and  Pettersson,  in  extensive  ex- 
perimental M'ork,  discovered  conditions  Avhich,  they 
believe,  explain  the  lack  of  correspondence  between 
serum  properties  and  natural  immunity.  In  the 
serum  of  the  relatively  immune  dog  and  chicken 
they  found  bactericidal  amboceptors  but  no  com- 
plement; hence,  the  serum  could  show  no  bacteri- 
cidal action  in  the  test-glass.  If,  however,  leuco- 
cytes from  the  same  animals  were  added  to  the 
serum,  the  latter  became  bactericidal.  It  may  be 
assumed  that  in  the  course  of  infection  the  ambo- 
ceptors are  activated  by  complement  which  is  dis- 
charged from  the  leucocytes.  The  failure  of  the 
bactericidal  substances  of  the  rabbit's  serum  to 
protect  the  animal  was  ascribed  to  the  ability  of 
the  tissues  to  absorb  the  amboceptors  (cited  from 
Sobernheim).  Their  work  is  of  sufficient  im- 
portance to  demand  repetition. 

Wright  has  shown  the  importance  of  the  opsonins 
for  phagocytosis  of  the  anthrax  bacillus. 

Eecovery  from  spontaneous  infection  is  said  to 


332  IXFECTIOX    AXD    HIMUNITY. 

confer  a  degree  of  iiuinunitv.  wliii'li,  lidwever,  is 
not  permanent. 

Vaccination.  Artificial  immunitj'  may  be  produced  by  active 
or  passive  immnnization.  The  first  attempts  at 
vaccination  were  made  in  1880  by  Toussaint,  who 
injected  the  blood  of  infected  animals  after  it  had 
been  heated  to  55  degrees  for  ten  minutes.  The 
bacilli  were  thus  attenuated,  but  they  were  able  to 
form  spores  subsequently  and  vaccination  Avas  not 
always  successful.  Pasteur  used  two  vaccines.  Vac- 
cine I  consisted  of  a  culture  which  was  attenuated 
by  growth  at  42°  C,  and  which  contained  no 
spores.  Vaccine  II  was  a  virulent  culture,  and  was 
injected  in  from  ten  to  fourteen  days  after  vac- 
cine I.  Its  use  is  said  to  have  caused  a  decrease 
in  anthrax  in  heavily  infected  districts,  with  a  con- 
sequent decrease  of  the  disease  in  man.  Various 
modifications  of  the  vaccines  of  Pasteur  have  been 
devised  by  others,  and  they  seem  to  be  equally  suc- 
cessful. In  some  instances  killed  bacilli  and  the 
-products  of  bacterial  growth  have  been  used  with 
less  success.  The  Anthracase-Immunprotcidin  of 
Emmerich  and  Lowe  is  not  of  established  value. 
Immune  serum  for  therapeutic  purposes  is  pre- 

and  Prpphy-  pared  by  immunization,  first  with  killed  or  atten- 
uated cultures  and  then  with  virulent  strains.  The 
two  vaccines  of  Pasteur  may  be  used.  Although 
the  serum  has  been  shown  to  have  fairly  strong 
protective  powers,  it  is  of  less  value  when  used  for 
curative  purposes.  It  produces  no  effect  after  the 
blood  stream  has  been  invaded  by  the  bacilli.  Its 
greatest  value  is  for  the  protection  of  herds  when 
anthrax  has  declared  itself.  In  man  it  has  been 
used  chiefly  in  the  treatment  of  malignant  pustule 
in  which  the  prognosis,  even  without  specific  treat- 


laxis. 


MALTA    FEVER.  333 

ment,  is  not  unfavorable.  The  best  known  serums 
are  those  of  Sclavo,  prepared  from  the  goat  and  ass, 
of  Mendez  and  Deutsch.  The  properties  on  which 
the  value  of  the  serums  depends  are  unknown.  So- 
bernheim.  is  very  positive  in  stating  that  the  bac- 
tericidal power  of  an  animal's  serum  is  not  in- 
creased by  immunization  or  infection,  and  the  ex- 
istence of  an  antitoxin  is  not  recognized.  As  in 
some  other  instances  immunization  may  cause  an 
increase  in  opsonins  which  would  render  the  serum 
effective  by  its  power  to  cause  increased  phagocy- 
tosis. 

The  method  of  Sobernheim,  that  of  mixed  active  ^ixed  immuni- 
and  passive  immunization,  seems  to  be  successful  guftfnatkin.'^^' 
as  a  prophylactic  measure.  The  vaccine  consists 
of  a  mixture  of  antiserum  and  bacilli.  Immune 
and  even  normal  serums  at  times  may  agglutinate 
the  anthrax  bacillus,  but  the  reaction  is  inconstant, 
and  the  ability  of  an  immune  serum  to  cause  ag- 
glutination is  no  index  of  its  protective  power.  Ag- 
glutination is  somewhat  difficult  of  determination 
because  of  the  tendency  of  the  bacillus  to  grow  in 
the  form  of  chains. 

II.    MALTA  FEVER. 

Malta,  Mediterranean  or  undulant  fever,  discovered 
in  the  Island  of  Malta,  is  also  seen  among  British 
troops  at  Gibraltar,  and  cases  have  been  discovered 
in  the  Caribbean  Sea,  Porto  Eico,  in  Hongkong  and 
in  Manila.  Historically,  it  has  been  traced  to  the 
beginning  of  the  nineteenth  century,  but  it  was 
first  described  as  an  independent  disease  by  Mars- 
ten  in  1859.  It  is  said  to  be  extending.  The  dis- 
ease usually  runs  a  long  course,  which  is  somewhat 
typhoidal  in  character,  and  there  may  be  one  or 


33-t  i\ri:rrio\  wn   nniryiTY. 

more  rclai)so.s.  The  si)lerii  is  ciilarjicd.  hut  tlie  in- 
testines are  not  involved. 

"It  is  distinofiiished  rrom  typlidid  hv  its  loni;'  (hi- 
ration,  sonietinies  extemliug  over  many  months; 
by  a  course  of  fever  exhibiting  marked  iiiuhda- 
tions;  by  the  occurrence  of  copious  perspirations; 
by  the  frequent  appearance  of  rheumatic  articular 
disorders  as  well  as  l>y  neuralgia  and  inflammation 
of  the  scrotum  and  epididymis"  (Scheuhe).  It 
occurs  especially  in  the  summer  months. 

Basset-Smith  found  the  serum  in  practically  all 
stages  of  the  disease  and  in  convalescence  to  have 
little  or  no  bactericidal  power  for  the  coccus.  Nor- 
mal serum  appeared  to  be  more  bactericidal  than 
that  of  the  patients,  although  such  an  action  was 
often  missed  in  normal  serum.  Wright  says  that 
normal  human  serum  is  devoid  of  bactericidal 
power  for  the  organism.  Basset-Smith  also  con- 
cluded that  the  phagocytic  power  of  the  patient's 
leucocytes  is  less  than  in  the  case  of  normal  leuco- 
cytes. According  to  Wright,  the,  organism  "is  em- 
inently sensible  to  the  opsonic  action  of  the  nor- 
mal serum,"  under  the  influence  of  which  it  is 
taken  up  in  large  numbers  by  the  leucocytes. 

Agglutination  by  the  serums  of  patients  takes 
place  in  dilutions  varying  from  1-300  to  1-2000 
or  even  as  high  as  1-GOOO.  Agglutinins  develop 
fairly  early  in  the  course  of  the  infection,  and  the 
test  is  of  great  diagnostic  importance. 

Bacilhts  meUtensis,  discovered  by  Bruce  (1887) 
in  the  spleen  of  patients  who  had  died  of  the  dis- 
ease, is  a  minute  organism,  slightly  oval  in  shape. 
According  to  Gordon,  it  possesses  one  flagellum, 
rarely  two  or  four,  and  is  slightly  motile.  The 
l)aeilius  is  found  in  pure  cultures  in  the  spleen, 


MALTA    FEVER.  335 

which  is  greatly  cnlargecl.  Its  growth  in  culture 
media  is  very  slow. 

It  is  thought  that  infected  water  may  be  one 
means  of  transmission  of  the  disease.  Laboratory 
infections  have  occurred  through  small  wounds. 
The  disease  is  not  transmitted  from  person  to  per- 
son. 

Up  to  the  present  time  the  monkey  is  the  only 
animal  known  to  be  susceptible  to  artificial  infec- 
tion, although  the  organism  may  have  a  low  degree 
of  virulence  for  rabbits  and  guinea-pigs  (Durham). 

One  attack  confers  immunity,  which  may  disap- 
pear, however,  after  some  time  (Hughes). 

An  immune  serum  which  was  prepared  by 
Wright  is  said  to  influence  favorably  the  course  of 
the  disease. 


GROUP  III. 


Acute  infectious  diseases  in  which  acquired  im- 
munity of  prolonged  duration  is  not  established. 
In  some  instances  soluble  toxins  are  produced 
which  are  of  unknown  importance  in  infection 
(staphylococcus,  streptococcus).  Some  of  the  or- 
ganisms contain  rather  strong  endotoxins  (pneu- 
mococcus,  gonococcus),  whereas  in  others  a  reason- 
able basis  for  their  infectiousness  is  not  at  hand. 
In  some  instances  immunization  causes  increased 
resistance  to  infection  (staphylococcus,  streptococ- 
cus), whereas  this  property  has  not  been  fully 
demonstrated  in  others.*  The  serums  of  immun- 
ized animals  may  or  may  not  be  protective  for 
other  animals.  Those  organisms  which  cause  sys- 
temic infection  give  rise  to  clinical  leucocytosis 
"  (except  influenza).  Local  inflammations  are  ac- 
companied by  the  accumulation  of  polymorphonu- 
clear leucocytes. 

I.     PNEUMOCOCCUS    INFECTIONS — PNEUMONIA. 

Organisms  No  onc  Organism  is  the  exclusive  cause  of  any 
Pneum'lfnia^  ouc  t}^e  of  pncumonia,  except  perhaps  the  viruses 
of  syphilis  and  tuberculosis.  Any  microbe  which 
causes  pneumonia  can  also  set  up  infla;mmations 
in  other  organs.  The  following  may  cause  acute 
pulmonitis:  Diplococcus  pneumonice.  Streptococ- 
cus pyogenes.  Staphylococcus  pyogenes^  bacillus  of 
Friedlander  (B.  pneumonice) ,  B.  infiuenzce,  B.  pes- 
tis,  B.  dipMher'm,  B.  typhosus,  B.  coli  communis, 

♦  This  point  is  diflScult  of  determination  when  an  organ- 
ism has  little  or  no  pathogenicity  for  animals  (influenza, 
gonococcus,  bacillus  of  Ducrey,   etc.). 


PNEUMOCOCGUS.  337 

and  Micrococcus  catarrhalis.  The  organisms  of 
tuberculosis,  actinomycosis,  the  virus  of  syphilis 
and  some  other  infections  cause  chronic  inflamma- 
tions of  the  lungs.  Some  of  these  organisms  have 
already  been  considered  and  others  will  be  dis- 
cussed later,  in  their  relation  to  pneumonia,  with- 
out, however,  entering  into  details  as  to  the  vari- 
ous types  of  the  disease.  The  Diplococcus  pneu-  Dipiococcus 
monice  is  the  commonest  cause  of  lobar  pneumonia.  Pneumoniae. 
It  produces  lobular  pneumonia  not  infrequently, 
and  has  been  found  as  the  only  organism  in  acute 
interstitial  pneumonia  (Weichselbaum). 

Friedlander  (1882)  found  that  capsulated  cocci 
were  present  constantly  in  the  exudate  of  pneumo- 
nia. Such  cocci  in  all  probability  represented  the 
organism  which  at  present  is  known  as  the  diplo- 
coccus of  pneumonia,  yet  the  cultures  which  he  ob- 
tained somewhat  later  showed  the  characteristics 
of  the  organism  now  loiown  as  the  bacillus  of 
Friedlander.  Fraenkel,  in  1884,  obtained  the  first- 
named  coccus  in  pure  culture,  and  his  investiga- 
tions, together  with  those  of  Weichselbaum  and 
many  others,  eventually  established  the  independ- 
ence of  the  tAvo  organisms. 

The  typical  pneumococcus  is  slightly  elongated,  Typical  and 
and  both  in  the  tissues  and  in  culture  media  it  suams."^*' 
grows  in  pairs.  Typically,  also,  the  pair  possesses 
a  capsule  which  is  present  constantly  in  the  tissues 
and  may  be  obtained  on  certain  culture  media 
(milk  and  serum).  It  is  non-motile,  non-flagel- 
lated, forms  no  spores  and  stains  by  Gram's  meth- 
od. Rather  scant  growth  occurs  on  the  ordinary 
culture  media  in  the  form  of  small  colonies  which 
resemble  those  of  the  streptococcus,  and  unless  spe- 
cial media  are  used  it  usually  can  not  be  carried 


338 


INFECTIOy    AXn    IMMIXITY. 


Confusion  with 
Streptococcus. 


Resistance. 


through  many  generations.  When  grown  in  si)n- 
tiim,  or  on  a  medium  wliicli  contains  ascitic  fluid, 
the  hlood  or  serum  of  man  or  some  favorable  ani- 
nuil,  its  virulence  may  be  preserved  for  some  time. 
By  growth  at  39°  C.  virulence  is  lost  rapidly. 
Strains  which  are  atypical  in  one  of  several  ways 
are  encountered.  They  may  show  low  virulence, 
may  grow  well  at  ordinary  temperatures  (the  typi- 
cal organism  not  doing  so),  may  produce  long 
chains  in  liquid  media,  or  may  grow  without  a 
capsule. 

Eecently  the  danger  of  confusing  tlie  pneumo- 
coccus  with  the  streptococcus  has  received  renewed 
attention,  and  newer  methods  of  differentiation 
render  it  extremely  probable  that  such  confusion 
has  occurred  in  the  past.  An  important  differen- 
tial method  is  that  of  cultivation  on  agar  plates 
which  contain  blood  (Schottmiiller)  ;  the  strepto- 
coccus produces  a  clear  zone  of  liemolyzed  corpus- 
cles about  its  colonies,  whereas  the  colonies  of  the 
pneumococcus  present  a  greenish  color  and  produce 
no  hemolysis.  In  using  this  test  Euediger  found  a 
surprising  number  of  pneumococci  in  normal 
throats,  whereas  previous  work  had  shown  them  to 
be  much  less  common  than  streptococci. 

In  spite  of  the  poor  viability  of  the  organism  on 
ordinary  culture  media,  it  is  fairly  resistant  to 
desiccation  and  sunlight,  especially  when  imbedded 
in  sputum.  It  is  possible  that  the  surrounding  spu- 
tum is  protective  and  that  the  well-formed  capsule 
which  the  coccus  possesses  as  a  parasite,  increases  its 
resistance.  Wlien  dried  and  powdered  it  is  much 
less  resistant,  being  killed  by  direct  sunlight  in 
about  an  hour.  Like  other  bacteria,  it  resists  dif- 
fuse sunlight  better  than  direct,  and  in  the  former 


PNEUMOCOCCUS. 


339 


may  live  for  as  long  as  fifty-five  days  in  a  drietl 
state  (Bordoni-Uffreduzzi,  cited  by  Weichsel- 
baum).  It  has  very  little  resistance  to  heat,  being 
killed  by  a  temperature  of  53°  C.  for  ten  minutes. 
No  characteristic  soluble  toxin  has  been  obtained,  Toxic 

.  '    Properties. 

although  more  or  less  poisonous  substances,  some 
of  them  of  a  chemical  nature,  have  been  described. 
Presumably  the  toxic  properties  reside  in  an  endo- 
toxin. The  pneumotoxin  of  F.  and  Gr.  Klemperer 
was  prepared  by  precipitation  with  alcohol.  The 
pneumococcus  is  a  pyogenic  organism  and  causes 
exudates  which  are  rich  in  fibrin.  Occasionally 
serous  rather  than  purulent  exudates  are  produced. 
Its  toxic  action  is  directed  toward  various  organs, 
and  it  is  doubtful  if  any  of  the  tissues  of  the  body 
are  non-susceptible.  Some  strains  are  supposed  to 
be  more  neurotoxic  than  others. 

The  susceptibility  of  animals  varies  greatly. 
Eabbits  and  mice  are  extremely  susceptible  and  are 
used  as  test  animals  for  the  identification  of  the 
organism.  Other  laboratory  animals  have  greater 
resistance,  and  the  pigeon  and  chicken  are  almost 
absolutely  immune.  In  susceptible  animals  a  rap- 
idly fatal  coccemia  or  more  or  less  extensive  local 
lesions  are  produced,  depending  on  the  virulence  of 
the  culture,  the  seat  of  inoculation  and  the  suscep- 
tibility of  the  animal.  In  rabbits  lobar  pneumonia 
has  been  produced  by  inoculation  into  the  pleura, 
trachea,  blood  stream  or  subcutaneous  tissue. 

The  pneumococcus  is  present  in  the  nose,  mouth  pccu 
and  pharynx  of  a  large  percentage  of  individuals. 
It  is  encountered  more  frequently  in  crowded  cities 
than  in  country  districts.  It  persists  for  weeks 
and  months  in  the  mouths  of  convalescents  from 
pneumonia,  and  it  reaches  the  mouths  of  those 


Susceptibility 
of  Animals. 


rrence 
in  the  Body 


the  Lungs. 


340  IXFECTION    AND    IMMUNITY. 

who  are  in  the  vicinity  oi'  pncunionics.  It  is  found 
frequently  in  the  conjunctiva  and  occasionally  in 
the  deeper  air  passages.  That  it  may  reach  the 
stomach  and  intestines  with  the  sputum  is  appar- 
ent, and  it  has  been  found  there  as  the  cause  of 
diphtheritic  enteritis,  a  condition  wliich  may  be 
followed  by  pncumococcus  peritonitis  or  general 
infection. 
Entrance  into  The  luugs  are  infcctcd  by  inhalation  of  the 
cocci.  Suspended  in  droplets  of  saliva  or  mucus, 
or  adherent  to  foreign  particles,  they  may  be  car- 
ried fairly  deeply  into  the  bronchial  tubes.  That 
they  ever  reach  the  alveoli  by  this  means  alone  is 
questioned  by  many.  Two  factors  would  seem  to 
prevent  their  being  carried  to  the  alveoli  by  cur- 
rents of  inspired  air :  First,  foreign  bodies  or  in- 
fected droplets  are  likely  to  strike  and  adhere  to 
the  walls  of  the  respiratory  passages  before  they 
have  traversed  a  great  length,  and  from  this  situa- 
tion may  again  be  carried  out  by  the  action  of  the 
ciliated  epithelium  or  coughing;  tlie  tortuous  pas- 
sages of  the  nose  and  its  hairs  and  moist  surfaces 
arrest  many  micro-organisms.  Second,  the  velocity 
of  the  inspired  air  is  greatly  reduced  or  is  nil  by 
the  time  the  particles  might  have  reached  the 
alveoli,  a  condition  which  renders  their  arrest  all 
the  more  probable.  Nevertheless,  pneumococci  do 
reach  the  alveoli,  and  by  some  it  is  supposed  that 
even  in  health  they  are  carried  there  more  or  less 
constantly  and  are  as  constantly  destroyed.  Occa- 
sionally they  have  been  found  in  the  parenchyma- 
tons  tissue  of  the  lungs  of  individuals  who  have 
died  of  other  than  pneumococcal  infections  or  of 
non-infectious  diseases.  In  order  to  show  that 
micro-organisms  may  be  carried  into  the  paren- 


PNEUMOVOCCUS. 


341 


genous  In- 
fection. 


chyma  by  inspiration  Nenninger  allowed  animals 
to  inhale  a  spray  containing  Micrococcus  prodigio- 
sus,  and  killing  the  animals  after  one-half  hour, 
was  able  to  cultivate  the  coccus  from  the  base  of 
the  lungs  where  only  alveoli  and  the  finest  bron- 
chial branches  were  present  (cited  by  Weichsel- 
baum) . 

Various  other  agencies  have  been  suggested  l)y  '-^^^^^^^"o""* 
which  the  cocci  may  be  carried  to  the  parenchyma- 
tous tissue.  For  example,  during  the  forced  res- 
piratory efEorts  which  accompany  coughing  they 
may  be  carried  from  the  bronchial  branches  into 
the  alveoli.  Or  the  organisms  having  reached  the 
bronchi,  may  be  carried  through  the  walls  of  the 
latter,  perhaps  by  the  leucocytes,  and  reach  the 
alveoli  directly  through  the  lymph  channels  or 
after  having  caused  infection  in 'the  peribronchial 
lymph  glands.  Others  express  the  opinion  that 
pneumonia  follows  blood  infection  in  many  or 
most  instances,  i.  e.,  that  the  infection  is  hemato- 
genous, the  cocci  having  reached  the  blood  in  some 
obscure  manner.  That  the  infection  may  be  hema- 
togenous is  shown  by  the  occasional  occurrence  of 
pneumonia  secondary  to  pneumococcus  infection  in 
other  parts  of  the  body. 

Knowing  the  fairly  constant  presence  of  pneu- 
mococci  in  the  upper  respiratory  passages  in  the 
normal  individual,  it  seems  certain  that  some  un- 
usual condition  must  arise  to  precipitate  infection 
of  the  pulmonary  tissue.  Concerning  the  nature 
of  these  conditions,  we  have  little  but  theories. 
They  may  rest  either  with  the  microbe  or  the  in- 
dividual, or  with  both.  The  pneumococci  which 
are  normally  on  the  mucous  surfaces  may  undergo 
an  increase  in  virulence,  or  more  virulent  organ- 


Conditions  for 

Infection. 


Decrease  of 
Resistance. 


342  IMJJCTWX    A.\D    IMMLNITY. 

isms  from  the  outer  world,  or  from  pneumonic  pa- 
tients, may  be  inhaled.  The  latter  condition  is  an 
important  one  in  relation  to  the  contagiousness  of 
pneumonia  and  the  development  of  epidemics. 
Park  and  Williams  found  a  larger  percentage  of 
virulent  organisms  in  the  sputum  of  pneumonics 
than  in  that  of  normal  persons.  It  is  possible  that 
the  pneumococcus  in  being  passed  from  one  patient 
to  another  undergoes  an  increase  in  virulence,  sim- 
ilar to  the  increase  which  may  be  obtained  by  pass- 
ing bacteria  through  animals. 

On  the  other  hand,  it  is  very  probable  that  es- 
sential changes  take  place  in  the  individual, 
changes  which  in  some  may  cause  the  lowered  re- 
sistance which  is  so  often  referred  to  as  a  condition 
for  infection.  Exposure  to  cold  has  long  been 
known  as  an  important  predisposing  factor,  al- 
though we  continue  in  ignorance  of  its  precise 
effects.  Animals  are  more  susceptible  to  pneumo- 
coccus infection  after  artificial  reduction  of  the 
body  temperature.  It  is  possible  that  a  lowered 
body  temperature  may  decrease  antibacterial  ac- 
tivities; that  the  activity  of  the  bactericidal  fer- 
ments of  the  plasma  or  of  the  leucocytes  may  be 
suppressed,  or  phagocytosis  may  be  inhibited  so 
that  organisms  which  reach  the  bronchi  and  peri- 
bronchial lymphatic  structures  are  allowed  to  pro- 
liferate. It  is  probable  that  in  health  the  leuco- 
cytes continuously  pass  through  the  bronchial  and 
alveolar  walls  where  they  may  englobe  foreign  par- 
ticles (coal  dust)  or  bacteria,  and  leucoc3^tes  are 
present  on  the  mucous  membranes  of  the  mouth 
cavity.  Following  exposure  and  the  reduction  of 
the  body  temperature,  or  following  the  prolonged 
inspiration  of  cold  air.  the  activity  of  the  phago- 


PNEUMOCOOCUS. 


343 


Other  Predis- 
posing Factors. 


cytes  may  be  inhibited  so  that  cocci  which  reach 
these  surfaces  are  not  ingested  and  continue  to 
proliferate,  or  the  same  conditions  may  decrease 
the  exudation  of  tlie  leucocytes  from  the  vessels. 
It  is  possible  also  that  the  activity  of  the  ciliated 
epithelium  is  reduced  similarly  so  that  the  cocci 
are  not  so  readily  carried  to  the  exterior. 

Extreme  exposure  is  not  always  followed  by 
pneumonia,  however,  and  not  all  cases  of  pneumo- 
nia are  preceded  by  exposure;  many  other  condi- 
tions may  predispose  to  infection,  as  a  lowered 
resistance  due  to  alcoholism,  other  infections  or  to 
non-infectious  processes.  That  certain  local  con- 
ditions may  favor  infection  is  indicated  by  the  fre- 
quency with  which  individuals  with  chronic  tuber- 
culosis of  the  lungs  die  of  pneumococcus  pneumo- 
nia, and  the  development  of  the  disease  in  areas 
of  hypostatic  congestion.  Age  is  of  influence.  "To 
the  sixth  year  the  predisposition  to  .pneumonia  is 
marked;  it  diminishes  to  the  fifteenth  year,  but 
then  for  each  subsequent  decade  it  increases" 
(Osier).  The  cause  of  these  variations  is  not 
known,  although  the  rise  in  later  years  may  be 
associated  with  increased  exposure. 

The  conditions  which  predispose  to  infection  are 
now  the  subject  of  active  study  in  many  labora- 
tories, and  the  commission  which  the  New  York 
Department  of  Health  has  established  for  the  study 
of  acute  respiratory  diseases  has  already  made  im- 
portant observations  as  to  the  prevalence  and  viru- 
lence of  pneumococci. 

Many  observers  have  found  pneumococci  in  the  complications, 
blood  in  a  large  percentage  of  the  cases,  and  recent 
work  by  Eosenow  indicates  that  the  blood  is  prob- 
ably infected  in  all  cases  at  some  stage  of  the  dis- 


344  INFECTION    AND    IMMUNITY. 

ease.  This  being  the  case,  the  i'requeuey  with  which 
pneumococcus  infections  occur  in  other  organs  as 
complications  of  pneumonia  is  readily  understood. 
Pleuritis  is  present  almost  constantly,  pericarditis 
frequently,  and  the  peritoneal  cavity  is  invaded  not 
infrequently  by  way  of  the  diaphragm,  with  general 
peritonitis  as  the  occasional  result.  In  pneumo- 
coccus pleuritis  tlie  exudate  is  frequently  of  a 
serous  character.  Endocarditis,  meningitis  and 
arthritis  are  frequent  complications.  Conjunctivi- 
tis, otitis  media,  cutaneous  or  subcutaneous  infec- 
tions, intramuscular  abscesses  and  osteomyelitis 
may  develop.  The  kidneys  and  liver  usually  show 
acute  degenerations. 

Diplococcus  pneumonia  occurs  as  a  complication 
in  typhoid,  diphtheria,  tuberculosis,  influenza,  ery- 
sipelas and  other  infections,  the  organism  of  the 
primary  infection  also  being  found  in  the  lungs. 
Not  infrequently  staphylococci,,  streptococci,  Mi- 
crococcus catarrliaUs,  or  the  bacillus  of  Friedland- 
er,  are  found  with  the  pneumococcus,  the  latter 
being  the  predominating  organism.  Eecent  work 
from  Phipps'  Institute  (Flick,  Ravenell  and  Er- 
win)  suggests  that  the  pneumococcus  ma}^  be  an 
exciting  cause  of  pulmonary  hemorrhage  in  the 
tuberculous. 
Prophylaxis.  Prophylactic  measures  are  largely  of  an  individ- 
ual character.  One  should  not  come  in  contact  un- 
necessarily with  those  suffering  from  pneumonia. 
The  susceptible  should  be  guarded  against  expos- 
ure; pneumonia  should  be  considered  as  a  conta- 
gious disease,  the  cases  isolated  as  sucli,  the  sputum 
disinfected,  and  rooms  cleaned  with  moist  antisep- 
tics rather  than  by  dusting  and  sweeping;  the  sick 
room    should   be   flooded   with   sunlight,   and   the 


PNEUMOGOCOUS. 


345 


mouths  of  convalescents  disinfected.  Expectora- 
tion in  public  places  should  be  limited.  To  what 
extent  the  dust-laden  atmosphere  which  prevails 
in  most  of  our  large  cities  is  a  factor  in  causing 
pneumonia  is  unknown.  Vaccination  is  not  yet 
an  established  procedure. 

It  is  probable  that  the  susceptibility  of  man  immunity  and 
varies  greatly.  Under  equal  conditions  of  expos-  susceptibility. 
ure  not  all  contract  pneumonia,  and  an  individual 
who  eventually  contracts  the  disease  may  have 
undergone  many  similar  exposures  previously. 
Klemperer  introduced  a  culture  of  the  pneumococ- 
cus  which  was  virulent  for  rabbits  imder  his  skin 
without  suffering  more  than  temporary  disturb- 
ance. 

Eecovery  seems  to  indicate  an  acquired  immun-  Recovery. 
ity  or  resistance  which  is  by  no  means  permanent, 
and  often  is  of  very  short  duration.  One  may  have 
as  many  as  eight  or  ten  attacks  of  pneumonia,  the 
intervals  between  attacks  being  from  three  to  five 
years  on  the  average  (Griswolle).  What  the  re- 
covery or  acquired  resistance  depends  on  is  un- 
known. The  marked  leucocytosis  of  pneumonia, 
and  the  known  phagocytic  power  of  the  leucocytes 
for  the  diplococcus,  suggest  strongly  the  impor- 
tance of  the  leucocytes  for  recovery.  The  serums 
of  convalescents  and  of  immune  animals  show  no 
increased  bactericidal  power  for  the  organism,  nor 
are  they  strikingly  antitoxic. 

Beginning  with  Fraenkel    (1886),  many  have  serum 
shown  the  possibility  of  increasing  the  resistance  and'opsonins 
of  susceptible  animals  to  the  pneumococcus  by  in- 
jecting first  dead  or  avirulent  and  then  virulent 
cultures ;  in  this  way  the  subjects  can  be  made  to 
withstand  many  multiples  of  the  minimum  fatal 


Phagocytosis. 


340  IXFECTWX    AM)    IMMUNITY. 

dose.  Culture  filtrates  and  precipitates  (the  pucu- 
motoxin  of  F.  and  G.  Klemperer)  have  been  used 
for  similar  purposes.  The  serum  of  immune  ani- 
mals, and  in  some  instances  of  convalescents,  has 
been  found  to  have  a  protective  effect  when  in- 
jected into  other  animals,  and  by  some  a  curative 
effect  is  claimed  when  the  serum  is  given  shortly 
after  infection.  Mennes  made  the  interesting  ob- 
servation that  "normal  leucocytes  only  become 
phagocytic  toward  pneumococci  when  they  are  lying 
in  the  serum  of  an  animal  immunized  against  this 
bacterium"  (Muir  and  Eitchie).  This  action  may 
have  been  due  to  the  effect  of  the  opsonins  which 
Wright  and  Douglass  have  shown  to  be  essential 
for  the  phagocytosis  of  pneumococci.  According 
to  iSTeufeld  and  Eimpau,  autipneumococcus  serum 
is  not  bactericidal,  but  through  the  influence  of 
bacteriotropic  substances  (opsonins  ?  )  which  it 
contains  renders  the  cocci  more  susceptible  to 
phagocytosis.^  Likewise,  Park  and  Williams  found 
antipneumococcus  serum  from  the  sheep  to  be 
protective  for  mice  and  to  stimulate  phagocytosis. 
The  correspondence  between  bacteriotropic  action 
and  protective  power  was  variable,  however,  so 
that  it  did  not  appear  certain  that  the  protective 
power  of  the  serum  was  due  entirely  to  its  influence 
on  phagocytosis.  We  are,  of  course,  not  sure  that 
events  in  the  animal  body  correspond  Avith  those  in 
the  test-glass. 

Some  of  the  serums  Avhich  have  been  prepared 
^"una^Fdn!  ^^^^^  been  used  therapeutically  in  man.     The  re- 
sults have  not  been  sufficiently  satisfactory  to  put 

1.  This  bacteriotropic  substance,  according  to  Neufeld, 
differs  from  tlie  opsonin  of  Wriglit  in  that  it  is  not  de- 
stroyed   by  low  degrees   of  heat. 


Serum  Therapy 


PNEUMOCOCaUS. 


347 


them  on  a  good  basis,  althougli  some  favorable  re- 
ports have  been  given. 

The  serum  of  Eoemer,  which  is  best  known  at 
the  present  time,  is  obtained  by  immunizing  dif- 
ferent kinds  of  animals  with  several  strains  of 
pneumococci.  The  receptor  apparatus  of  different 
strains  probably  differ;  hence,  a  serum  obtained 
by  immunization  with  several  strains  probably 
would  be  effective  against  a  large  variety  of  pneu- 
mococci. Furthermore,  since  different  animals 
may  respond  to  immunization  with  a  given  organ- 
ism by  the  formation  of  amboceptors  with  different 
complementophilous  haptophores,  a  theoretical  ad- 
vantage is  to  be  gained  by  mixing  immune  serums 
from  several  animals.  The  amboceptors  of  one  or 
more  of  the  serums  may  be  susceptible  to  activa- 
tion by  the  complement  of  the  patient's  body, 
whereas  if  only  one  serum  were  used  the  chance  of 
such  activation  would  be  decreased.  Passler,  in 
summing  up  the  results  obtained  in  the  treatment 
of  24  cases  with  this  serum,  finds  the  course  of  the 
disease  shortened,  the  temperature  reduced  and  a 
tendency  to  limit  the  extension  of  the  disease  to 
other  parts  of  the  lungs. 

The  serum  of  pneumonic  patients  shows  an  in- 
creased agglutinating  power  for  the  pneumococcus. 
The  maximum  is  reached  at  or  near  the  time  of 
crisis,  but  rarely  has  a  higher  value  than  1  to  50 
to  1  to  60  (Neufeld,  Eosenow).  It  disappears 
quickly  after  recovery.  In  immunized  animals  the 
agglutinating  power  may  be  pushed  to  much  higher 
limits.  Not  all  strains  yield  -agglutinins  equally, 
and  not  all  are  agglutinated  equally  by  the  same 
serum.  According  to  Collins,  pneumococci  fall 
into  different  groups,  depending  on  their  agglu- 


Serum  of 
Roemer. 


Agglutination. 


348  IM'EVnoX    AXD    niilUNITY. 

finable  properties;  the  same  author  detenniued 
the  presence  of  group  agglutinins  in  an  immune 
serum.  Neufeld  states  that  avirulent  strains  were 
not  agglutinated  by  the  serum  of  pneumonic  pa- 
tients. 

OTHER  INFECTIONS  BY  THE  PNEUMOCOCCUS. 

Complicating  infections  b}^  the  pneumococcus 
during  the  course  of  pneumonia  were  mentioned 
above.  They  may  occur  by  way  of  the  lymph 
channels,  as  in  pleuritis,  pericarditis  and  peritoni- 
tis (through  the  diaphragm),  by  continuous  exten- 
sion, as  in  infection  of  the  bronchi,  nose  and,  per- 
haps, the  middle  ear,  or  as  metastatic  infections 
following  the  invasion  of  the  blood  stream  by  the 
organisms.  It  is  undoubtedly  in  the  last  named 
manner  that  meningitis,  endocarditis,  arthritis, 
muscular  and  subcutaneous  abscesses  arise. 
Mode  of  Other  infections  by  the  pneumococcus  occur  in- 
dependent of  the  existence  of  pneumonia.  Such 
conditions  are  alveolar  abscesses,  conjunctivitis, 
dachryocystitis,  serpent  ulcer  of  the  cornea,  in- 
flammation of  the  middle  ear,  meningitis,  enteri- 
tis, rarely  peritonitis,  and  pneumococcus  septice- 
mia which  may  be  complicated  by  infection  in  vari- 
ous organs.  The  eye  is  exposed  to  infection  from 
without  and  the  ear  from  the  pharynx.  Primary 
jjneumococcus  meningitis  occurs  both  sporadically 
and  epidemically,  although  the  meningococcus  is 
a  more  frequent  cause.  The  organisms  may  gain 
entrance  through  the  middle  ear  or  nose,  or 
through  the  circulation  from  a  primary  focus  in 
another  organ,  perhaps  an  undiscovered  focus.  Pre- 
ceding and  during  meningitis  the  nose  is  not  in- 
frequently the  scat  of  pneumococcus  rhinitis,  and 


Infection. 


STREPTOCOCCUS.  349 

the  organisms  may  bo  carried  from  the  nose  to  tlie 
meninges  by  way  of  the  lymph  channels.  The 
blood  may  be  infected  secondarily.  Pneumococcus 
meningitis  is  almost  invariably  fatal.  The  organ- 
ism causes  chronic  meningitis  less  frequently  than 
the  meningococcus.  Infection  of  the  peritoneum 
may  follow  an  intestinal  infection ;  a  pure  pneumo- 
coccus infection  of  the  peritoneum  in  the  absence 
of  pneumonia  is  extremely  rare.  Pneumococcus 
infections  of  the  eye,  ear,  intestines  and  perito- 
neum are  likely  to  be  accompanied  by  other  or- 
ganisms. 

Pneumococcus  conjunctivitis  occurs  in  epidemic 
form  and  the  same  precautions  should  be  taken 
to  limit  it  as  for  the  limitation  of  influenza  con- 
junctivitis. 

Serpent  ulcer  of  the  eye,  a  progressive  phage- 
denic process  in  the  cornea,  has  the  pneumococcus 
as  its  essential  cause,  although  other  organisms 
may  be  present.  Eoemer  treats  the  condition  with 
an  antipneumococcus  serum  and  claims  that  he  is 
able  to  arrest  the  process  if  the  treatment  is  begun 
sufficiently  early.  The  serum  is  injected  beneath 
the  conjunctiva. 

II.   STREPTOCOCCI. 

When  wound  infections,  cases  of  septicemia  and  Discovery  of 
pyemia  were  first  studied  bacteriologically,  various  Pyoaemc  coccf, 
names  were  applied  to  certain  cocci  which  were 
found.  Such  were  the  Microsporon  septicum  of 
Klebs  and  the  Coccobaderia  septica  of  Billroth 
and  others.  Pasteur  recognized  such  organisms 
and  cultivated  them  at  an  early  date,  but  Ogsten, 
in  1880  to  1884,  using  the  newly-devised  technic 
of  Koch,  was  the  first  to  recognize  two  sorts  of 


350  IXFECTIOX    AND    IMMUNITY. 

pyogenic  cocci,  to  which  he  gave  the  names  of  strep- 
tococci and  staphylococci.  The  former  grew  in  tlie 
form  of  chains  and  the  hitter  in  chisters.  In  1883 
Felileisen  obtained  the  streptococcus  in  pure  cult- 
ures from  cases  of  erysipelas.  Rosenbach  deter- 
mined more  exactly  the  significance  of  streptococci 
in  wound  infections  and  septicemia,  and  gave  to 
the  organism  the  name  of  Streptococcus  pyogenes. 
Morphology.  The  typical  streptococcus  is  a  spherical  or 
spheroidal  cell,  about  one  micron  in  diameter, 
which  grows  in  the  form  of  chains  of  varying 
length.  Division  takes  place  in  one  direction 
only.  Variations  in  form,  such  as  diplococcus-like 
cells  in  pairs  or  chains,  or  elongated  cells  resem- 
l)ling  bacilli,  represent  accidental  stages  or  anoma- 
lies in  division.  Streptococci  commonly  appear  as 
diplococci  in  the  blood  and  tissues  of  the  infected. 
Unusually  large  cells  may  be  involution  forms. 
The  difficulty  of  distinguishing  the  pneumococcus 
from  the  streptococcus  has  been  mentioned.  At 
one  time  it  was  thought  that  streptococci  could 
be  separated  into  those  which  grew  in  long  chains 
(S.  long  us)  and  those  which  produce  short  chains 
(S.hrevis).  Although  these  names  are  still  used 
for  convenience,  they  are  not  well  grounded,  since 
the  length  of  the  chains  is  not  an  inherent  prop- 
erty; one  form  may  be  changed  into  the  other  by 
appropriate  methods  of  cultivation.  Similarly  the 
S.  erysipelatis  of  Eehleisen  is  not  a  specific  or- 
ganism for  erysipelas,  since  strains  from  other 
sources  are  able  to  cause  experimental  erysipelas 
in  man.  Streptococci  growing  in  short  chains  may 
be  cultivated  from  the  normal  mouth  cavity  and 
they  are  usually  of  low  virulence  for  animals.  On 
the  other  hand,  *S^.  longus  is  more  often  obtained 


STREPTOCOCCUS. 


351 


from  wound  infections,  septicemia  and  malignant 
tonsillitis.  Capsulated  strains  of  high  virulence 
are  occasionally  found  in  the  body.  Ordinarily, 
however,  streptococci  are  not  surrounded  by  a  cap- 
sule. The  Streptococcus  mucosus  capsulatus  may 
be  a  pneumococcus.  Although  streptococci  are  de- 
scribed which  do  not  stain  by  Gram's  method,  those 
with  which  we  are  concerned  invariably  react  posi- 
tively. Streptococci  are  never  motile,  possess  no 
flagellse  and  form  no  spores. 

Streptococci  grow  better  in  a  neutral  or  slightly  cultivation. 
alkaline  medium  than  in  one  of  acid  reaction,  but 
virulence  is  lost  rapidly.  They  may  be  cultivated 
indefinitely  in  media  which  contain  serum  or 
ascitic  fluid,  but  even  here  virulence  disappears 
gradually;  frequent  transplantation  is  necessary. 
In  bouillon  those  strains  which  produce  short 
chains  or  grow  as  diplococci  cause  a  diffuse  cloud- 
ing of  the  medium,  whereas  those  growing  in  long 
chains  sink  to  the  bottom,  leaving  a  clear  overly- 
ing fluid.  Streptococci  demand  little  oxygen,  all 
are  facultative  anaerobes  and  some  are  said  to  be 
obligate  anaerobes;  obligate  anaerobes  may  be  cul- 
tivated from  the  vagina  and  intestines.  The 
optimum  temperature  for  growth  is  37°  C. 

When  dried,  streptococci  live  for  from  ten  days 
to  several  weeks;  they  are  destroyed  more  quickly 
in  the  presence  of  sunlight.  Susceptibility  to 
antiseptics  depends  on  the  nature  of  the  medium 
in  which  they  are  suspended  or  imbedded.  When 
unprotected  by  bouillon  or  other  fluid  they  are 
killed  in  a  few  seconds  by  1/1000  corrosive  sub- 
limate and  3  per  cent,  carbolic  acid  (Fehleisen)  ; 
when  in  bouillon,  by  1/1500  corrosive  sublimate 
and  by  1/200  carbolic  acid  in  fifteen  minutes.   Ly- 


Resistance. 


352  lyFECTION    AXD    IMMUNITY. 

ing  on  a  mucous  surface,  where  they  are  imbedded 
in  mucus  or  tissue  fluids,  they  are  protected 
against  antiseptics  to  some  extent.  They  are  fairly 
resistant  to  heat,  being  destroyed  by  a  temperature 
of  70°  to  75°  C.  in  one  hour  (v.  Lingelslieim). 
Virulence.  Strcptococci  vdiy  widcly  in  their  pathogenicity. 
Cultures  which  are  entirely  non-pathogenic  for 
animals  are  frequently  cultivated  from  nature  and 
from  man.  As  a  rule,  however,  the  long  chains 
obtained  from  pathological  processes  in  man  are 
pathogenic  for  rabbits  and  mice.  Their  virulence 
is  very  labile,  and  by  passage  through  suitable  ani- 
mals (rabbit,  mouse)  it  may  be  pushed  to  a  very 
high  point;  in  doing  this,  however,  the  original 
virulence  of  the  culture  undergoes  modifications. 
For  example,  Marmorek  so  increased  the  virulence 
of  one  strain  that  the  milliardth  part  of  a  c.c.  was 
fatal  for  rabbits,  but  it  had  lost  its  pathogenicity 
for  man,  as  shown  by  inoculations  into  carcino- 
matous patients.  Hence  the  pathogenicity  of  cul- 
tures for  animals  is  not  a  good  index  of  their  viru- 
lence for  man.  Those  which  produce  long  chains 
in  bouillon  are  more  pathogenic  than  those  form- 
ing short  chains  (v.  Lingelsheim). 

Eabbits  and  mice  are  the  most  susceptible  ani- 
mals. The  rat,  guinea-pig  and  cat,  and  larger  ani- 
mals, as  the  horse,  goat  and  sheep,  are  less  sus- 
ceptible. A  bouillon  culture  of  which  .01  to  1.0 
c.c.  will  kill  a  mouse  or  rabbit  in  from  one  to  four 
days  is  considered  of  high  to  moderate  virulence. 
Virulent  cultures  cause  systemic  infection,  regard- 
less of  the  method  of  inoculation.  Less  virulent 
cultures  produce  changes  which  are  more  localized 
in  character  and  which  may  heal :  abscesses,  areas 
of  necrosis  and  erysipelatous  inflammations. 


STREPTOCOCCUS.  353 

The  properties  on  which  the  virulence  of  strepto-  Endotoxin. 
cocci  depends  are  little  understood.  The  conflict 
of  opinion  concerning  many  points  probably  de- 
pends on  the  use  of  different  strains  of  the  organ- 
ism in  experimental  work.  The  amount  of  endo- 
toxin which  virulent  strains  contain  is  subject  to 
great  variations.  Aronson  found  practically  none 
in  the  killed  cells  of  a  very  virulent  strain.  It. 
seems  probable  that  the  endotoxin  is  rather  sus- 
ceptible to  heat,  since  cultures  which  are  killed 
by  mild  methods,  as  by  chloroform,  are  more  toxic 
than  those  whicli  are  killed  by  heat.  The  filtrates 
of  old  bouillon  cultures  are  more  or  less  toxic.  A 
strong  "toxin"  was  prepared  by  Marmorek  by 
growing  a  virulent  strain  in  a  mixture  of  serum 
and  bouillon  for  three  months  and  filtering  the 
culture.  More  recently  he  uses  a  medium  contain- 
ing glycocol  and  leucin.  Toxic  precipitates  from 
fluid  cultures  have  also  been  obtained.  Bouillon 
filtrates  of  virulent  cultures  after  two  to  fourteen 
days  of  growth  have  low  toxicity  (Aronson). 

Besredka,  and  later  Gr.  P.  Euediger,  showed  that  streptocoiysin 
virulent  streptococci  produce  a  hemolytic  toxin  Toxin!*"^***^^*"^ 
when  gro\\Ti  in  various  heated  serums.  Euediger 
proved  that  this  hemolysin  (streptocoiysin)  is  a 
true  toxin,  possessing  a  haptophorous  and  toxo- 
phorous  structure.  This  discovery  has  an  im- 
portant bearing  on  the  fact  that  the  blood  in  fatal 
streptococcus  infections,  especially  in  rabbits,  is 
often  more  or  less  laked.  Streptocoiysin  is  de- 
stroyed by  a  temperature  of  70°  C.  in  two  hours, 
by  peptic  digestion,  deteriorates  rapidly  at  ordi- 
nary temperatures,  and  is  non-dialysable.  Certain 
normal  serums  contain  antistreptocolysin  (Eue- 
diger).     Another    significant    discovery   by   Eue- 


'Soi  IXFECTIOy    AXD    IMMUXITY. 

diger  is  that  virulent  strains,  when  grown  in  soruni 
and  ascitic  fluid,  produce  a  substance  -\vhieli  kills 
leucocytes  and  inhibits  phagocytosis.  This  may 
explain  the  failure  of  leucocytes  to  take  up  virulent 
organisms,  whereas  non-virulent  strains  are  readily 
phagocytized.  Lingelsheim  states  that  strains  cul- 
tivated from  subacute  or  chronic  processes  produce 
•more  soluble  toxin  (nature  unknown)  tlian  highly 
virulent  strains.  Not  all  toxic  fdtrates  contain 
streptocolysin,  the  hemolysin  being  independent  of 
other  toxic  constituents  (Simon).  Lingelsheim 
concludes  that  the  infectiousness  of  streptococci  is 
not  explained  by  the  toxic  properties  which  have 
been  demonstrated.  He  lays  stress  on  their  resist- 
ance to  the  bactericidal  activities  of  the  tissues  and 
tissue  fluids.  It  is  safe  to  say  that  up  to  the  ])res- 
ent  time  the  essential  toxin  of  the  streptococcus 
has  not  been  demonstrated. 
Pathologic       Streptococci  are  the  frequent  cause  of  wound  in- 

Processes 

fections,  the  most  common  cause  of  lymphangitis 
and  dift'use  inflammations  of  the  subcutaneous  and 
intermuscular  connective  tissues  (cellulitis),  endo- 
metritis and  puerperal  septicemia,  endocarditis 
and  tonsillitis,  are  often  the  exciting  organisms 
in  pneumonia  (lobular,  usually),  bronchitis, 
meningitis,  inflammations  of  the  serous  surfaces 
(pericardium,  pleura,  peritoneum  joints),  enteritis 
and  suppurative  processes  in  the  middle  ear.  They 
are  the  exclusive  cause  of  erysipelas,  which  occurs 
naturally,  and  serious  attempts  have  been  made  to 
show  tliat  they  arc  etiologic  factors  in  scarlet 
fever  and  rheumatic  fever.  The  streptococcus  is 
the  most  common  organism  found  in  the  lesions 
of  impetigo  contagiosa,  although  it  may  be  mixed 
with  other  bacteria,  especially  tlio  staphylococcus. 


STREPTOCOCCUS.  355 

Occurring  as  mixed  infections  in  pneumonia,  tu- 
berculosiS;  scarlet  fever,  enteritis  and  other  proc- 
esses, they  cause  grave  and  often  fatal  complica- 
tions. 

Xot  all  streptococci  are  able  to  cause  erysipelas.  Erysipelas. 
and  a  streptococcus  cultivated  from  a  case  of  ery- 
sipelas is  not  able  to  cause  the  disease  in  all  indi- 
viduals. Furthermore,  cultures  obtained  from 
other  sources  (phlegmon)  may  produce  the  dis- 
ease. (Koch  and  Petruschky.)  Koch  produced 
an  erysipelatous  inflammation  with  a  staphylococ- 
cus. It  has  been  suggested  that  streptococci  which 
cause  erysipelas,  rather  than  some  other  process, 
do  so  because  of  some  peculiarity  in  their  virulence 
or  in  the  resistance  of  the  individual,  or  perhaps 
both.  Another  suggestion  is  that  this  type  of  in- 
fection depends  on  some  peculiaritj^  in  the  skin 
and  subcutaneous  tissue  of  the  susceptible.  The 
conditions  are  obscure.  The  infection  atrium  is 
not  always  known.  In  facial  erysipelas  entrance 
probably  is  gained  through  the  mucous  membrane 
of  the  nose  in  many  instances.  Erysipelas  is  a 
wound  infection  in  most  or  all  instances,  although 
the  atrium  often  escapes  observation.  The  cocci 
lie  principally  in  the  hniiph  spaces  and  interspaces 
of  the  connective  tissue.  They  are  rarely  to  be 
cultivated  from  the  scales  or  the  fluid  of  blisters, 
but  may  be  obtained  from  skin  which  is  excised 
from  the  border  of  the  inflamed  area.  (Fehleisen.) 
They  probably  are  not  excreted  through  the  un- 
broken skin. 

Erysipelas  is  an  inflammation  of  the  superficial  Lymphangitis. 
honphatics  of  the  skin,  while  in  hTnphangitis  the 
deeper  lymphatics  are  involved.     Thrombosis   of 
the  lymphatic  vessels,  congestion  of  the  adjacent 


3.")*!  IXFJX'TIOX     AM)    /.!/ 1/r.\  77'1'. 

blood  vessols,  cau.-ini;'  I'cddciU'd  ^^l•(■nks  ;uid  local 
lu'inolysis  (?).  arc  disliimuishing  local  I'caturos. 
Metastases  occur  to  adjacent  lyinpli  glands  and 
the  infection  niav  become  general.  Jn  this  process, 
as  well  as  in  wound  infections,  thrombosis  of  the 
ailjaccut  vessels  mav  occur,  \\liicli  may  be  the  first 
step  in  the  production  of  pyemia  with  multiple 
points  of  infection.  Cellulitis  may  also  be  caused  by 
the  staphyloeoecus  alone  or  infection  with  the  lat- 
ter may  be  superimposed  on  a  ])rimary  streptococ- 
cus cellulitis. 

Pneumonia.  Pneumonia  |)i"oduc-i'd  by  the  streptococcus  may 
either  be  primary  or  secondary  to  infection  in 
other  parts  of  the  body.  Characteristically,  it  re- 
send)les  the  lobular  type  in  the  occurrence  of 
multiple  foci,  which  present  a  smooth  surface  on 
section  and  are  very  rich  in  cells.  It  occurs  less 
frequently  as  the  cause  of  lobar  consolidation,  and 
very  frequently  as  a  mixed  infection  in  pneumo- 
nias caused  by  the  pneumococcus  and  other  organ- 
isms. Streptococcus  infection  of  the  lungs  in  pul- 
monary tuberculosis  is  a  serious  and  frequent  com- 
plication of  the  latter  disease.  It  produces  a  septic 
condition,  involves  adjacent  healthy  tissue,  and  its 
role  in  causing  consolidation  and  liquefaction  of 
the  tissues  predisposes  of  hemorrhages.  In  cultures 
the  streptococcus  is  said  to  inhibit  the  growth  of 
the  tubercle  bacillus,  and  it  has  occasionally  been 
noted  that  the  tuberculous,  after  suffering  a  strep- 
tococcus infection  (erysipelas),  show  an  improved 
condition ! 

Meningitis.  Primary  streptococcus  meningitis  is  rare  or  of 
doubtful  occurrence.  It  frequently  is  secondary 
to  otitis  media,  and  has  been  noted  following  ton- 


HTRHI'TOCOaCUH. 


357 


Vagina  and 
Uterus. 


sillitis,  facial  erysipelas,  pneumonia,  endocarditis 
and  as  part  of  a  pyemic  process. 

Streptococci  are  perhaps  the  most  important  Enteritis, 
cause  of  enteritis  in  children,  the  inflammation 
often  being  membranous  and  accompanied  by 
desquamation  of  the  epithelium  and  by  hemor- 
rhages. It  is  not  infrequently  followed  by  peri- 
tonitis and  septicemia.  Virulent  organisms  prob- 
ably reach  the  intestines  through  milk  in  many 
instances.  Escherich  found  streptococci  in  nearly 
every  sample  of  milk  which  he  examined.  Digest- 
ive disturbances  due  to  other  causes  predispose  to 
infection.  The  organisms  are  nearly  always  pres- 
ent in  the  intestines  of  the  adult,  but  cause  en- 
teritis less  frequently  than  in  children. 

The  normal  vagina  does  not  offer  a  good  cul- 
ture medium  for  patliogenic  bacteria,  although 
streptococci  are  occasionally  found  there.  They 
occur  more  frequently  in  those  who  have  borne 
children.  The  vagina  tends  to  purify  itself  me- 
chanically and  by  the  acid  nature  of  its  secretions. 
If  the  secretion  for  any  reason  becomes  alkaline, 
as  in  catarrhal  conditions,  or  if  it  contains  blood 
and  serum,  which  provide  a  good  culture  medium, 
virulent  streptococci  proliferate.  Infection  takes 
place  through  denuded  surfaces  and  tears ;  endome- 
tritis, metritis,  parametritis,  salpingitis,  peri- 
tonitis and  sepsis  may  follow.  Thrombosis  of  the 
blood  vessels  may  be  followed  by  the  development 
■of  pneumonic  foci. 

Streptococci  are  probably  always  present  on  the   Upper  Respira- 
tonsils,  the  mucous  membrane  of  the  mouth,  very 
frequently  in  the  sputum  and  not  infrequently  on 
the  mucous  membrane  of  the  anterior -nares.     Pre- 
sumably they  proliferate  under  inflammatory  con- 


358  IXFIJCTIOX    A\D    IMMUNITY. 

ditioiis  from  wliatover  c-auso,  finding  in  tlie  serum 
and  plasma  wliich  exude  a  medium  favorable  for 
growth  and  the  development  of  virulence.  Thej^ 
are  of  great  significance  in  severe  local  inflamma- 
tions, as  in  diphtiieria  and  scarlatina,  and  when 
general  resistance  is  lowered,  as  in  typhoid,  typhus, 
variola,  measles,  etc.  Lingelsheim  characterizes 
their  relation  to  diphtiieria  as  follows:  they  injure 
the  tissues  locally,  penetrate  beneatli  the  uiciu- 
brane  into  the  tissues  and  take  part  in  the  forma- 
tion of  the  membrane;  they  increase  the  virulence 
of  the  diphtheria  bacillus;  alone,  or  in  conjunction 
mth  the  diphtheria  bacillus,  they  may  invade  the 
lungs,  causing  bronchopneumonia,  or  enter  tlie 
circulation  and  injure  various  organs,  but  particu- 
larly the  kidneys.  Their  method  of  entering  the 
lungs  from  the  upper  respiratory  passages  probably 
is  similar  to  that  involved  in  pneumococcus  infec- 
tion. Furthermore,  having  obtained  a  footing 
in  the  pharynx,  for  example,  they  may  reach  the 
bronchi  and  perhaps  the  alveoli  by  extension  along 
the  surface. 

Streptococci  are  usually  the  essential  organisms 
in  follicular  tonsillitis,  are  frequently  found  in 
alveolar  abscesses,  but  in  both  instances  may  be 
mixed  with  other  organisms,  especially  the  staphy- 
lococcus and  pneumococcus.  Streptococci  in  tlie 
throat  may  appear  in  diplococcus  form  in  fresh 
preparations.  Beginning  primarily  in  the  nose, 
tonsils  or  pharynx,  streptococcus  infection  may 
extend  to  the  adjacent  sinuses,  the  middle  ear, 
meninges,  or  through  the  tonsils  may  cause  sys- 
temic infection  with  endocarditis  as  a  frequent 
complication. 

Tlie  endocarditis  caused  by  streptococci  usually 


HTREPTOVOCCUH. 


359 


Rheumatic 
Fever. 


is  vegetative  in  character,  but  may  be  ulcerative,  Endocarditis. 
and  may  result  in  metastatic  foci  of  infection 
(e.  g.,  septic  infarcts).  Infarcts  from  strepto- 
coccus endocarditis  are  not  always  infected,  how- 
ever. Not  infrequently  the  vegetations  contain 
staphylococci  as  well  as  streptococci. 

Since  1867,  when  Salisbury  described  a  fungus 
which  he  called  Zymo host's  translucens,TsxQiiy  micro- 
organisms have  l^een  described  and  cultivated  from 
the  joints,  blood,  endocarditic  and  pericarditic 
lesions  and  from  the  tonsils  in  acute  articular 
rheumatism.  Among  them  were  the  "Monadinen" 
of  Klebs  (1875),  short  bacilli  by  Wilson  (1885) 
and  others,  staphylococci  and  streptococci  by 
Weichselbaum  (1885)  and  by  many  others,  and 
an  anaerobic  bacillus  resembling  that  of  anthrax 
by  Achalme  (1890).  Streptococci  have  been  found 
more  frequently  than  other  organisms.  The  ba- 
cillus of  Achalme  acquired  considerable  prominence 
at  one  time,  being  found  in  rheumatism  in  a  num- 
ber of  cases,  but  it  has  been  found  since  in  other 
conditions,  and  normally,  and  Achalme  himself 
gave  up  his  original  claims  for  its  etiologic 
significance.  The  organism,  possibly,  is  identical 
with  B.  aerogenes  capsulatus  of  Welch  (Harris). 
Many  of  the  observations  are  of  little  value,  since 
the  cultures  were  made  postmortem,  when  contami- 
nations and  agonal  invasions  by  other  organisms 
could  not  be  excluded.  The  conditions  were  very 
confusing,  however,  since  the  injection  of  pure 
cultures  occasionally  produced  arthritis,  peri- 
carditis and  endocarditis  in  animals.  This  was 
the  case  with  a  short  anaerobic  bacillus  or  diplo- 
bacillus  cultivated  by  Thiroloix,  and  by  Triboulet, 
Coyon  and  Zadoc  (1897). 


300  INFECTION    AND    nfMUNITY. 

In  1897-98  Triboulet  and  C'ovon  cultivated  from 
the  blood  of  tive  cases  of  rheumatic  fever  a  di])lo- 
coceus,  pure  cultures  of  which  caused  arthritis, 
endocarditi:^.  etc..  in  rabbits.  Similar  oliservatinns 
liave  been  niadr  by  Wcst|ibal.  W'asscniiaiiii  ami 
^[alkoir,  Poynton  and  Paine,  i^eaton  and  Walker 
and  others,  and  the  possibility  of  producing  lesions 
characteristic  of  rheumatic  fever  by  the  inocula- 
tion of  pure  cultures  into  rabbits  lias  been  well  es- 
tablished. Although  the  organism  was  called  a 
diplococcus  by  the  discoverers,  it  can  not  be  dis- 
tinguished from  the  ordinary  streptococcus  pyo- 
genes by  cultural  tests.  These  discoveries  do  not, 
however,  put  this  particular  streptococcus  on  a 
satisfactory  l^asis  as  the  cause  of  the  disease,  since 
streptococci  liom  various  sources  are  able  to  cause 
experimental  arthritis  in  rabbits  (Cole,  Harris). 
It  seems  that  virulent  streptococci  from  whatever 
source  have  a  predilection  for  serous  surfaces.  This 
is  apparent  from  the  frequency  witli  which  the 
joints,  endocardium,  etc.,  are  involved  in  strepto- 
coccus septicemia  in  man.  The  view  of  Singer 
and  of  Menzer  that  "acute  rheumatism  is  simply 
one  of"  the  many  manifestations  of  streptococcus 
invasion"  (Harris),  finds  some  justification  in 
the  streptococcus  tonsillitis  witli  which  the  dis- 
ease iisually  begins,  the  recovery  of  streptococci 
from  the  lesions  and  the  production  of  these  lesions 
in  rabl)its  by  the  injection  of  pure  cultures.  The 
fact  remains,  liowever,  that  streptococci  can  not 
always  be  cultivated  from  the  lesions  of  rheumatic 
fever;  hence  it  is  possible  that  the  organism  may 
exist  as  a  mixed  infection  with  more  or  less  con- 
stancy, and  that  the  real  cause  is  as  yet  unknown 

fpiiiiiip). 


STREPTOCOCGU^.  361 


Relation  of 
Streptococci  to 


The  theory  that  scarlet  fever  is  of  streptococcus 
etiology  has  been  held  particularly  by  Babes,  ScarTetTever. 
Klein,  Moser,  Gordan  and  Baginsky  and  Sommer- 
feld.  Some  have  held  that  streptococci  isolated 
from  the  disease  show  distinctive  properties  and 
deserve  the  name  of  Streptococcus  scarlatina' .  This, 
however,  is  not  agreed  to  by  most  bacteriologists, 
the  organisms  not  differing  from  streptococci  ob- 
tained from  various  sources.  The  organisms  are 
not  found  constantly  in  the  erythematous  eruption. 

Virulent  streptococci  are  found  on  the  tonsils 
almost  invariably  in  scarlet  fever.  In  65  per  cent, 
of  the  cases  a  membrane  is  formed  (Ranke),  and 
this  is  often  due  to  the  streptococcus,  which  is 
sometimes,  however,  associated  with  diphtheritic 
infection.  The  frequency  with  which  streptococci 
invade  the  blood  during  scarlet  fever  is  related  to 
the  severity  of  the  disease.  Occasionally  they  are 
found  in  mild  cases,  which  run  a  short,  uncompli- 
cated course,  but  "more  frequently  in  severe  and 
protracted  cases,  in  which  there  also  may  develop 
local  complications  and  clinical  signs  of  general 
infection,  such  as  joint  inflammations"  (Hek- 
toen).  Baginsky  and  Sommerfeld  found  strepto- 
cocci in  the  blood  and  organs  of  each  of  eighty- 
two  fatal  cases.  Hektoen  states,  however,  that 
streptococcemia  is  not  necessarily  present  in  fatal 
cases. 

At  the  present  time  there  is  not  sufficient  ground 
for  considering  streptococci  as  the  specific  agent 
in  scarlet  fever,  although  they  are  undoubtedly  the 
cause  of  the  most  frequent  and  serious  complica- 
tions. The  mortality  of  the  disease  probably  is 
greatly  raised  by  mixed  infections  with  the  strepto- 
coccus. 


3G2 


IM'EOriON    AND    IMMUNITY. 


Beneficial 
lafluences. 


Effect  on 
Sarcoma. 


Streptoeofcus  filtrates  or  cultures  may  cause  de- 
generative changes  in  the  spinal  cord  (Honien 
and  Laitineu). 

Certain  strains  of  streptococci  are  said  to  exer- 
eise  a  curative  eU'eel  in  experimental  anthrax. 
Emmerich  and  di  Mattei  found  that  by  intra- 
venous injection  of  the  cocci  rabbits  could  be  saved 
from  an  anthrax  infection  which  otherwise  would 
prove  fatal  in  forty-eight  hours.  This  result  can 
not  always  be  obtained,  and  it  may  be  that  only 
certain  strains  have  this  etfect  (Zagari,  cited  by 
Lingelsheim).  It  is  noted  occasionally  that  lupus 
improves  or  actually  heals  following  an  attack 
of  erysipelas.  A  reputed  effect  of  a  similar  nature 
in  tuberculosis  of  the  lungs  was  mentioned  above. 

The  rather  old  observation  that  an  attack  of 
erysipelas  often  causes  a  decrease  in  the  size  of 
malignant  tumors,  especially  sarcomas,  received 
some  confirmation  from  the  experimental  work  of 
Fehleisen.  With  the  hope  of  reproducing  erysipe- 
las with  pure  cultures,  Fehleisen  had  inoculated 
streptococci  into  those  suffering  from  such  tumors. 
Among  six  patients  so  inoculated,  a  decrease  in  the 
size  of  the  tumor  was  noted  in  five.  Killed  cul- 
tures were  tried  without  effect.  Coley's  mixture 
of  killed  cultures  of  the  streptococcus  and  Bacillus 
jyrodigiosus  received  rather  extensive  trial  as  a 
substitute  for  living  cultures  of  the  streptococcus, 
and  in  many  instances  improvement  and  even 
cures  have  been  reported.  Others  have  had  no 
favorable  results.  Senn  used  the  preparation  in 
twelve  cases  of  inoperable  sarcoma  "with  negative 
results."  The  Bacillus  prodigiosus  is  supposed  in 
some  way  to  increase  the  efficacy  of  the  strepto- 


m'RFJ'TOVOVCUH.  363 

COCCUS  toxin;  it  contains  a  toxic  protein.     These 
toxins  seem  to  have  no  influence  on  carcinomas. 

Concerning  the  natural  susceptibility  and  im-  yjJ^5J"jj^j"j"*' 
munity  of  man  to  infections  with  the  streptococcus 
little  is  known.  It  seems  probable  that  the  un- 
impaired mucous  surface  resists  invasion  by  the 
organisms  which  occur  constantly  in  the  mouth 
cavity;  the  physical  protection  of  the  intact  sur 
face,  the  rapid  desquamation  of  epithelium,  the 
rapid  excretion  with  the  saliva,  the  inhibiting  in- 
fluence of  the  saliva  on  the  proliferation  of  bac- 
teria and  the  destruction  of  bacteria  by  the  leuco- 
cytes which  constantly  appear  on  the  mucous  sur- 
face are  probably  important  factors  in  this  local 
resistance.  Congestion  of  these  surfaces,  espe- 
cially the  tonsils,  from  any  cause,  as  from  ex- 
posure, or  the  occurrence  of  some  other  infection, 
as  may  be  the  case  in  scarlet  fever,  may  lower  the 
local  protective  powers.  And,  as  stated,  the  serum 
and  plasma  which  exude  in  simple  (?)  catarrhal 
conditions  or  other  inflammations,  provide  a  me- 
dium which  favors  the  growth  and  development  of 
virulence  by  streptococci. 

Concerning  the  conditions  which,  in  the  body, 
antagonize  infection,  we  are  largely  in  the  dark. 
It  has  been  impossible  to  demonstrate  antitoxic 
and  bactericidal  substances  in  the  normal  serum 
of  man.  Streptococci  grow  freely  in  fresh  normal 
serum  which  contains  no  leucocytes.  (Weaver  and 
G.  F.  Euediger.)  Phagocytosis  of  streptococci 
first  came  under  the  observation  of  Metchnikoff, 
who  in  1887  noted  it  as  a  striking  occurrence  in 
erysipelas.  Only  the  microphages  took  up  the  cocci. 
The  marked  lucocytosis  which  is  noted  clinically 
suggests,  but  of  course  does  not  prove,  that  the 


364  INFECTIOX    AM>    /  1/ l/r.\77')'. 

leucocytes  tako  an  active  pari  in  llic  destruction 
of  the  cocci.  Hxperiuiental  Avork  showing  such  a 
relationship  is  not  lacking,  however.  Bordet  con- 
cluded that  all  the  protection  which  guinea-pigs 
and  rabbits  show  against  streptococci  is  due  to 
the  phagocytes.  In  actual  infection  streptococci 
have  often  been  found  within  the  leucocytes  of  the 
blood  and  inflammatory  exudates.  (G.  F.  Rue- 
digcr.)  Xon-virulent  or  weakly  virulent  strains 
are  phagocytized  more  readily  than  the  virulent  in 
experimental  work.  Ruediger  also  demonstrated 
conclusively  that  the  streptococci  taken  up  by  poly- 
morphonuclear leucocytes  may  be  killed  by  the  lat- 
ter. Hence  the  evidence  in  favor  of  a  protective 
role  by  the  leucocytes  is  more  than  presumptive. 
Ruediger  suggests  the  importance  of  the  leuco- 
cytic  toxin  of  the  streptococcus  for  the  develop- 
ment of  infection.  It  may  either  kill  the  leuco- 
cytes or  cause  negative  chemotaxis,  and  under  these 
conditions  proliferation  of  the  cocci  nuiy  proceed. 
Acquired  The  streptococcus  usually  is  classed  with  those 
organisms,  infection  with  which  does  not  cause  the 
development  of  lasting  imijiunity.  A  certain 
amount  of  immunity  probably  is  established,  how- 
ever. This  is  suggested  by  the  results  of  Fehlei- 
sen,  who  could  not  always  cause  second  attacks 
of  erysipelas  by  tlie  inoculation  of  pure  cultures 
into  the  susceptible.  It  is  also  suggested  by  the 
ease  with  which  relatively  high  resistance  can  be 
produced  in  animals  by  brief  immunization.  A 
streptococcus  infection  of  the  horse  which  occurs 
naturally  ("Druse")  is  said  to  produce  immunity 
which  lasts  for  a  year  or  two. 

One  may  immunize   animals   cithci-   witli   toxic 
filtrates  or  with  killed  and   liviim'  cultures.     The 


Immunity. 


STREl'TOCOCCUii. 


305 


filtrates  are  inueli  less  effective  in  producing  iin-   immunization 

T    •       j^i        1  1       01  Animals. 

mnnity  than  the  hacterial  cells,  and  m  the  hands 
of  nianv  ]io  innmmity  Avliatever  could  be  estab- 
lished. 

A  number  of  dili'erent  principles  liave  been  fol- 
lowed in  immunizing  with  cultures.  It  seems  that 
virulent  strains  cause  a  higher  degree  of  immunity 
and  a  serum  of  higher  protective  power  for  other 
animals  than  strains  of  low  virulence.  On  this 
account  Marmorek,  and  also  i\.ronson,  immunize 
horses  with  streptococci,  the  virulence  of  which  has 
been  pushed  to  a  very  high  point  by  passing  them 
through  rabbits.  Strong  resistance  is  induced  by 
this  method,  and  the  immune  serum,  particularly 
that  of  Aronson,  shows  distinct  protective  power 
for  other  animals.  Such  serums,  however,  have 
the  highest  protective  power  against  the  particu- 
lar strain  which  was  used  for  immunization,  al- 
though the  serum  of  Aronson  is  not  devoid  of  pro- 
tective powers  against  other  pathogenic  strains. 
Concerning  the  serum  of  Marmorek  there  are  di- 
vergent opinions.  In  the  hands  of  Marmorek  it 
is  highly  protective  in  animal  experiments;  others 
have  found  it  without  value.  The  method  of  Mar- 
morek and  of  Aronson  rests  not  only  on  the  basis  MuiUplicity 
that  strains  of  the  highest  virulence  will  give  the  «f streptococci. 
strongest  serums,  but  also  on  the  assumption  of 
the  unity  of  all  pathogenic  streptococci.  If  all 
are  alike  in  their  biologic  and  pathogenic  proper- 
.  ties,  a  serum  which  protects  against  one  should 
protect  against  all.  As  pointed  out,  there  is  at 
present  not  sufficient  ground  for  considering  the 
streptococci  of  erysipelas,  scarlet  fever,  rheuma- 
tism, sepsis,  etc.,  as  independent  species.  By  cul- 
tivation and  passage  it  is  possible  to  so  modify  any 


30G  INFECTIOX    .1\7>    IMMIMTY. 

one  of  them  that  it  is  imlisi  iimuisliiililc  from  the 
others,  on  the  basis  of  iiioi|)hologv  and  patho- 
genicity. On  the  other  liand  they  are  not  all 
itlentical  in  some  very  iiii|i(M-tant  properties.  For 
example,  not  all  strains  prixliiee  hemolysin  to  the 
same  degree,  and  they  differ  greatly  in  their  sus- 
ceptibility to  the  action  of  an  agghitinating  serum. 
We  have  also  to  remember  that  pathogenicity  for 
animals  is  not  a  reliable  index  of  patliogenicity  for 
man.  From  these  confusing  conditions  we  can 
only  regard  the  question  of  unity  or  multiplicity 
of  streptococci  as  an  open  one.  \vl)icli  may  ho  tlo- 
cided  by  future  investigations. 
Univalent  and  The  scrums  of  Marmorck  and  Aronson  are  uni- 
Serums.  \alent  serums,  a  single  strain  being  used  for  im- 
munization. Certain  investigators.  l)elieving  in 
the  multiplicity  of  streptococci,  utilize  several 
strains  in  immunization.  The  serum  of  Denys  is 
obtained  by  immunizing  with  several  strains  the 
virulence  of  which  has  been  artificially  increased. 
Such  a  serum  would,  theoretically,  have  a  wider 
range  of  action  than  a  univalent  serum ;  it  is  poly- 
valent. Having  in  mind  the  fact  that  passing  a  cul- 
ture through  rabbits  increases  tlic  virulence  of 
the  organism  for  the  rabbit,  l)ut  alters  its  virulence 
for  the  original  host  (man),  Tavel,  Moser  and 
Menzer  prepare  serums  on  a  dilTerent  basis. 
Tavel  employs  several  strains  of  streptococci  cul- 
tivated from  pathological  processes  in  man,  avoid- 
ing such  alterations  in  virulence  as  would  be  caused 
by  passing  the  cultures  through  animals.  On  the 
assumption  that  scarlet  fever  is  a  streptococcus 
disease,  j\Ioser  immunizes  horses  with  strains 
(about  twenty)  which  are  cultivated  from  cases 
of  scarlet  fever.     In  a  similar  manner,  Menzer, 


STREJ'TOfJOC'CUH. 


36i 


Protection. 


supposing  that  rlieiiiDatic  fever  is  a  streptococcus 
infection,  immunizes  with  a  number  of  strains  cul- 
tivated from  the  tonsils  of  cases  of  rheumatism. 
Both  Moser  and  Menzer  avoid  passage  in  order  to 
retain  the  original  biologic  properties  of  the  cul- 
tures. 

In  animal  experiments,  some  of  these  serums,  serum 
and  particularly  that  of  Aronson,  have  exhibited 
strong  protective  powers.  Aronson's  serum  in 
doses  of  0.0004  to  0.0005  c.c.  protects  a  mouse 
against  ten  fatal  doses  of  the  streptococcus  given 
twenty-four  hours  later  than  the  serum.  A  serum 
of  which  0.01  c.c.  protects  against  a  dose  known 
to  be  fatal  is  considered  of  normal  strength.  The 
present  serum,  then,  is  of  tAventy-  to  twenty-five- 
fold value.  In  some  instances  animals  can  be 
saved  when  the  serum  is  used  some  hours  after 
infection,  but  this  period  is  a  brief  one. 

Statements  concerning  the  value  of  antistrepto-  serum 
coccus  serums  in  treating  human  infections  are 
very  conflicting.  The  serum  of  Marmorek  has 
been  given  more  general  trial  than  any  other,  and 
the  results  have  not  been  satisfactory.  Favorable 
effects,  such  as  the  lowering  of  temperature  and 
improvement  in  the  general  condition,  have  been 
reported,  but  the  serum  possesses  no  distinct  cura- 
tive power  in  established  infections.  Koch  and 
Petruschky  deny  that  it  has  a  prophylactic  power 
in  experimental  erysipelas.  Escherich,  by  using 
the  serum  of  Moser,  and  Baginsla^  by  using  that 
of  Aronson,  observed  a  shortening  of  the  course, 
a  reduction  of  the  fever  and  general  improvement 
in  cases  of  scarlet  fever.  Moser  claims  that  it  re- 
duces the  mortality  of  the  disease.  The  use  of 
anti  streptococcus  serum  in  the  treatment  of  scarlet 


Therapy. 


Scarlet 
Fever. 


308  IM'KCnoX    AM)    niMi.MTY. 

'  rover  doi's  luit  roiiiinit  oiu'  to  tlio  streptococcus 
etiology  of  tlie  ilisease,  Inil  i-;itlu'r  to  the  impor- 
tance of  streptococcus  coni})lications  ;  lu'iuc,  if  the 
(hinder  of  these  complications  can  he  rediu'cd  hy 
antistreptococcus  serum  its  use  is  justilied.  It 
renuiins  for  future  work  to  demonstrate  to  our 
satisfaction  that  it  has  such  value. 

What  has  lieeii  said  eoiireniinii'  the  t  I'cat  iiient  of 
Rheumatism,  scarlet  fcvcr  with  the  serums  of  Moser  and  Aron- 
son  also  a))])lies  to  the  treatment  of  rheumatism 
w  ith  the  seniiii  of  ]\Ienzer.  Favorable  reports  have- 
appeared  conc-erning  its  value,  l)ut  a  sufficient  mass, 
of  experience  has  not  accumulated  to  permit  of 
satisfactory  judiiment.  "80  much  appears  from, 
observations  in  uuin  that  the  different  streptococcus^ 
serums  are  harmless"  (Dieudonne). 

As  nearly  as  can  be  learned  at  present,  anti- 
Properties  strcptococcus  scrum  is  protective  (and  cura- 
erum,  ^j^.^  (  ?)  )  bccausc  of  its  ability  to  stimulate  phago- 
cytosis, rather  than  l)ecause  of  serum  antitoxins 
or  bacteriolysins.  This  was  indicated  by  the  ob- 
servations of  Bordet  in  animal  experiments,  in 
which  marked  phagocytosis  of  streptococci  took 
place  in  the  peritoneal  cavity  of  immunized  ani- 
mals, but  verv  little  in  normal  animals.     A  sinii- 

Stimulation  of    ,  i-i-        '  i     t     ■        n        ±      j       ^ 

Phagocytosis.  I'Av  condition  was  iiotcd  HI  tlic  tcst-glass  experi- 
ments of  Denys  and  van  der  Yelde.  A  mixture 
of  normal  rabbit  serum  and  leucocytes  showed 
very  little  phagocytosis  of  streptococci,  whereas 
the  addition  .of  antistreptococcus  serum  caused 
active  phagocytosis,  w^ith  death  of  the  cocci.  The 
presence  of  a  definite  substance  in  the  serum  which 
stimulated  phagocytosis  was  conceived  by  van  der 
Yelde  and  also  by  Lingelsheim.  It  was  heat-re- 
sistant   (62°   to  65°    C),  and  was  not  destroyed 


STREPTOCOCCUS.  369 

by  dilute  acids  and  alkalies  (cited  byLingelsheim). 
Hence  its  resistance  is  greater  than  the  opsonins 
of  Wright  and  Douglass,  but  perhaps  not  greater 
than  the  bacteriotropic  substances  of  ISTeufeld.  It 
is  probable  that  some  of  these  substances  are  heat- 
resistant  and  others  heat-susceptiljle. 

The  agglutinability  of  streptococci  from  differ-  Agoiutination. 
ent  sources,  and  even  from  the  same  source,  varies 
a  great  deal.  Also  the  normal  serums  of  man  and 
animals  have  a  variable  agglutinating  power  for 
different  strains  of  streptococci.  By  immunization 
with  a  given  strain  the  agglutinating  power  is  in- 
creased, but  not  uniformly  for  all  strains.  Com- 
monly the  strain  used  for  immunization  is  agglu- 
tinated more  strongly  than  heterologous  strains, 
the  latter  sometimes  undergoing  no  agglutination 
whatever.  These  variations  do  not  depend  on  dis- 
coverable differences  in  the  cocci  or  the  diseases 
which  they  produce.  A  given  antistreptococcus 
serum  does  not  agglutinate  equally  all  streptococci 
from  cases  of  scarlet  fever  (Weaver).  Also  strep- 
tococci vary  greatly  in  their  ability  to  stimulate 
to  the  formation  of  agglutinins.  On  the  whole 
those  which  produce  long  chains  are  more  suscep- 
tible to  agglutination  and  yield  stronger  serums 
than  those  with  short  chains.  (Aronson,  Tavel, 
V.  Lingelsheim. )  By  passage  the  agglutinating 
properties  undergo  rather  complex  changes.  The 
organism  then  produces  a  stronger  agglutinating 
serum  and  is  agglutinated  more  readily  by  this 
serum  than  the  same  strain  which  liad  not  been 
passed  through  animals.  If  passage  is  discon- 
tinued it  reverts  to  its  former  condition. 

The  variations  are  such  that  the  agglutination 


37U  l\ri:cTI()\    AM)    I M  Ml  MTV. 

vractioii  is  of  little  or  no  \;iliu'  in  (litVcrcmiatiiig 
tliUVront  tyju's  of  strt'ptofoc-ii. 

As  to  tlu'  c-linii-al  value  of  tlu'  Icsi  lor  \\\v  di-.x^j;- 
nosis  of  srarU't  iVviT,  the  i-oucliisidus  of  Weaver 
may  be  cited : 

1.  Of  streptococci  cultivated  ri'om  eases  of  sear- 
latiua,  some  are  agglutinated  In  almost  all  sear- 
latinal  sera,  but  at  dilutions  varying  from  1/GO 
to  1/4000;  others  are  agglutinated  by  the  same 
sera  with  less  constancy  and  at  lo\v(.'i-  dilutions,  and 
many  are  not  agglutinated  at  all. 

2.  Streptococci  cultivated  from  cases  of  scar- 
latina arc  agglutinated  by  sera  from  cases  of  lobar 
pneumonia  and  erysipelas  at  about  the  same  dilu- 
tions as  by  scarlatinal  sera,  and  in  the  case  of  ery- 
sipelas even  at  higher  dilutions. 

3.  The  same  appears  to  be  true  of  typhoid  fever 
serum,  so  far  as  limited  tests  indicate,  and  to  al- 
most the  same  extent  of  puerperal-fever  serum. 

4.  The  agglutination  reaction  between  the 
streptococci  cultivated  from  cases  of  scarlatina  and 
the  serum  from  cases  of  scarlet  fever  is  in  no  way 
specific,  and  can  not  be  of  any  value  as  a  means  of 
diagnosis. 

By  growing  streptococci  on  a  medium  which 
contains  serum  (serum  bouillon),  they  form  fewer 
and  shorter  chains  and  are  better  suited  for  ag- 
glutination tests. 

III.       STAniYLOCOCCI. 

Staph5dococci  are  spherical  cells  from  0.7  to  0.9 
microns  in  diameter,  typically,  and  l)y  light  stain- 
ing are  often  seen  to  consist  of  two  hemispheres, 
which  are  separated  by  a  delicate  cleft.     In  pus 

they  are  found  in  small  gi'oups  of  two  to  nine  or 


,rrM'if)ij>('0(jcus. 


371 


Ferments. 


ten,  ocasioiially  as  (lijjiocoeci.  tetrads  or  very  short 
chains. 

They  are  luxuriant  growers  on  nearly  all  media  Cultivation  and 
which  are  suitable  for  bacteria,  preferring,  how-  erties. 
ever,  a  slightly  alkaline  reaction.  Growth  is  best 
in  the  jDresence  of  oxygen,  but  proliferation  occurs 
in  its  absence.  Sputum,  serum  and  ascitic  fluid 
are  favorable  media,  and  in  the  last  two  the  cocci 
may  be  agglutinated.  An  alkaline  reaction  is  pro- 
duced in  litmus  milk,  and  the  casein  is  precipitated 
and  partly  digested.  The  production  of  a  proteo- 
lytic ferment  is  shown  by  liquefaction  of  gelatin 
and  the  formation  of  a  clear  zone  about  the  colo- 
nies when  grown  in  plates  which  contain  coagulat- 
ed serum  (Loeb,  cited  by  ISTeisser  and  Lipstein). 
Albumen  is  changed  into  peptone.  Loeb  distin- 
guishes between  a  ferment  which  liquefies  gelatin 
(gelatinase,  a  "collolytic'-  ferment),  and  one  which 
digests  albumen  (tr3'ptic  ferment).  Gelatinase  is 
present  in  staphylococcus  filtrates  and  normal 
serums  are  rich  in  antibodies  for  it.  A  fat-splitting 
ferment  (lab  ferment)  is  also  present  in  the 
filtrates.  The  fact  that  the  pus  which  is  produced 
in  staphylococcus  infection  does  not  coagulate  may 
be  due  to  the  action  of  the  proteolytic  ferment, 
which  digests  the  fibrinogen. 

Van  der  Velde  had  noted  in  1894  that  "staphy- 
lotoxin" (staphylococcus  filtrates)  cause  hemoly- 
sis. Neisser  and  Wechsberg,  in  1901,  by  growing 
the  organisms  in  bouillon  of  suitable  alkalinity, 
obtained  hemolytic  filtrates,  giving  the  name  of 
staph3dolysin  to  the  hemol3^tic  principle.  The  hemo- 
lytic action  of  the  staphylococcus  is  readily  seen 
in  cultures  on  blood-agar  plates;  a  zone  of  hemo- 
Ivsis  forms  about  the  colonies.    Ervthrocvtes  of  the 


Staphylolysin. 


372  IXFECTIOX    AM)    IMMUNITY. 

rabbit,  when  placed  in  bouillon  cultures,  undergo 
hemol3-sis.     Stapliylotoxin  also  produces  hemolysis 
in  the  living  body.     The  maximum  production  of 
staphylolysin   occurs   after  a  growth   of   nine    to 
fourteen    days    in    alkaline    bouillon,    and    nearly 
all   pathogenic  strains  yield   it.   wlietlicr   aureus, 
albus  or  citreus.     It  is  not  formed  by  non-patho- 
genic strains.     The  toxin  is  destroyed  by  exposure 
to  a  temperature  of  56°  C.  for  twenty  minutes.    A 
specific    antitoxin    is   present    in    many   normal 
serums   and  may  be  increased   by  immunization 
with  the  toxin  or  the  living  organisms. 
Leucocidin.       In  1894  van  der  Velde  found  in  the  pleural 
exudates  caused  by  inoculation  with  killed  cultures 
of  the  staphylococcus  a  substance  which  is  toxic 
for  leucocytes,  causing  them  to  swell  and  the  nuclei 
to  disappear.     This  substance  is  called  leucocidin. 
It  is  also  produced  in  culture  media,  but  the  ability 
to  form  it  is  not  so  widely  distributed  as  in  the 
case  of  the  hemolysin.    Leucocidin  is  a  true  toxin, 
like  the  hemolysin;  most  normal  serums  contain 
antileucocidin,  and  the  latter  is  increased  by  im- 
munization   with    the    toxin.*      The    suggestion 
is  a  natural  one  that  leucocidin  may  be  a  factor  in 
combating    phagocytosis    in    infections    with    the 
etaphylococcus.        Neisser     and     Wechsberg     de- 
vised  a   "bioscopic   method"   of   determining   the 
cytocidal  action  of  the  toxin.     Living  leucocytes, 
like  other  living  cells,  have  the  power  of  decoloriz- 
ing methylene  blue  when  oxygen  is  excluded.   The 
destructive  action  of  the  toxin  on  the  leucocytes 
is  indicated  by  the  failure  of  this  reduction  when 
the  toxin  is  mixed  with  the  cells. 

*  Leucocidin   and   staphylolysin   will   not   yield   antitoxins 
when  their  activity  has  been  destroyed  by  heat. 


staphylococcus'^. 


373 


Old  culture  filtrates  (two  to  three  weeks)  show  Toxic 
a  rather  high  degree  of  toxicity  for  animals,  pro- 
ducing extensive  degeneration  of  the  convoluted 
tubules  in  the  kidney,  a  degeneration  which  is 
somewhat  selective;  hemorrhages  into  the  in- 
testinal mucosa;  degeneration  of  the  ganglionic 
cells,  and  fever.  According  to  Levaditi,  a  mast- 
cell  leucocytosis  develops.  The  nature  of  the  fever- 
producing  substance  is  unknown.  The  toxicity  of 
filtrates  is  said  to  be  destroyed  by  a  temperature 
of  56°  C. 

Cultures  of  the  staphylococcus  killed  by  heat  Endotoxinf?) 
show  little  toxicity,  hence  the  question  of  the  ex- 
istence of  an  endotoxin  is  on  no  better  basis  than 
in  relation  to  the  streptococcus.  It  is  possible  that 
the  heat  required  to  kill  the  organisms  destroys  the 
endotoxin  as  well,  as  the  soluble  toxins  mentioned 
above.  The  virulence  of  the  organisms  has  no 
direct  relationship  to  the  hemolysin  or  leucocidin, 
or  the  toxicity  of  the  filtrates.  Very  pathogenic 
strains  may  produce  a  filtrate  of  little  or  no 
toxicity.  It  seems  then  that  the  essential  patho- 
genic agent  of  the  organism  is  unlcnown;  as  in 
the  case  of  the  streptococcus,  its  infectiousness  may 
depend  on  its  ability  to  resist  the  antibacterial  ac- 
tivities of  the  body  (phagocytosis,  ,  bacterioly- 
sis (?)  ),  which,  of  course,  is  a  very  indefinite 
assumption.  Wliat  part  the  leucocidin  plays  in 
this  resistance  is  not  definitely  known. 

The  many  varieties  of  the  staphjdococcus  are 
differentiated  on  the  basis  of  pathogenicity,  pig- 
ment formation,  liquefaction  or  ndn-liquefaction 
of  gelatin,  and  other  cultural  properties.  The 
alhus  differs  from  the  aureus  only  in  its  inability 
to  form  pigment,  and  it  can  not  be  made  to  ac- 
quire  this    property.      Pigment    is    formed    most 


Varieties  of 
Staphylo- 
coccus. 


374  /\ri:'"ri()\    i  \ /;  /i/ i/rv/v  r. 

abundantly  on  potato,  whereas  little  is  rornied 
on  blootl  serum.  Other  ])ignient-rorniing  varieties 
are:  .S*.  cereus  fiarus.  S.  pi/ogencs  citreus,  S.  scar- 
laliitii.'<  and  Micrococcus  lirinaio'dcs.  The  <S'.  cpi- 
dc  nil  id  is  a  lb  us  of  Welch  is  of  low  virulence.  Weich- 
selbaum  obtained  a  S.  endocardititis  rugatus  from 
a  case  of  endocarditis.  Xot  all  of  tliese  varieties 
produce  soluble  toxins.  The  pigment  of  S.  aureus 
is  an  excretion  product  which  is  fonncd  <»nly  in 
the  presence  of  oxygen.  It  is  insoluble  in  water, 
soluble  in  alcohol  and  ether,  and  gives  the  reac- 
tion of  a  lipochrome  (i.  e.,  the  pigment  may  be 
saponified  and  gives  the  lipocyanin  reaction  in 
which  the  pigment  turns  blue  when  ti-eated  with 
concentrated  sulphuric  acid). 
Resistance  Aside  from  wide  individual  variations,  the  re- 
sistance of  staphylococci  to  heat  depends  on  the 
concentration  of  the  suspension,  the  nature  of  the 
medium  (whether  water,  gelatin  or  pus),  and 
whether  the  test  is  a  dry  or  wet  one  (Neisser  and 
Lipstein).  Eighty  degrees  centigrade  for  one-half 
(o  one  hour  kills  them  under  all  conditions,  and 
(>0°  C.  for  one-half  hour  kills  many  strains  when 
suspended  in  bouillon.  They  are  not  killed  by  re- 
peated freezing  and  thawing,  and  are  very  resist- 
ant to  desijccation.  When  in  the  form  of  fine  dust 
they  die  in  twenty-eight  days  (Kirstein).  Resist- 
ance to  the  action  of  sunlight  is  variable;  some 
strains  are  killed  in  from  three  to  five  hours. 

Staphylococci  have  fairly  high  resistance  to  anti- 
septics; when  dried,  corrosive  sublimate  (1/1000) 
kills  them  in  two  to  three  hours,  and  when  im- 
bedded in  pus  thirteen  to  sixteen  hours  are  re- 
quired (Ottaviano).  Methyl  alcohol,  tincture  of 
green  soap  and  methyl  violet  are  relatively  good 
disinfectants.      "Methyl    violet     in     a   dilution    of 


8TAPHYL0C0CCUH. 


375 


1/10,000  kills  them  in  five  to  fifteen  minutes 
(Stilling).  Formalin  readily  hinders  develop- 
ment, but  its  bactericidal  power  is  low.  It  is 
difficult  or  impossible  to  sterilize  wounds  infected 
with  the  staphylococcus  by  means  of  antiseptics. 

Staphylococci  are  very  widely  distributed  in  na- 
ture and  are  to  be  found  constantly  in  the  super- 
ficial layers  of  the  epidermis  (*S^.  epidermidis  al- 
hus). 

In  infections  the  staphylococcus  attracts  large  Leucotacticand 
numbers  of  leucocytes,  and  the  pus  does  not  coagu-  substances. 
late.  The  substance  which  attracts  leucocytes  is 
heat-resistant,  since  killed  cultures  will  cause 
abscesses.  In  all  but  the  most  superficial  lesions 
a  characteristic  result  of  infection  is  that  of  cell 
necrosis  and  the  liquefaction  of  tissues.  IsTeisser 
and  Lipstein  state  that  the  necrotizing  substance 
is  a  soluble  toxin,  since  culture  filtrates  cause 
marked  necrosis  of  the  internal  organs  when  in- 
jected (liver,  heart,  kidney).  "Hence  in  staphylo- 
mycosis we  can  distinguish  two  active  substances 
(von  Lingelsheim),  the  leucotactic  substance  in 
the  bodies  of  the  cocci  and  the  more  important 
soluble  staph3dotoxin  which  exercises  not  only 
a  local  but  also  a  general  toxic  action  on  the  body" 
(Xeisser  and  Lipstein). 

Davidson  produced  amyloid  degeneration  in 
rabbits  and  mice  by  the  injection  of  living  cultures. 
This  was  confirmed  by  Lubarsch,  who  found  the 
condition  most  readily  produced  in  the  chicken 
and  with  more  difficulty  in  the  mouse,  rabbit  and 
dog.  It  rarely  results  if  suppuration  is  avoided. 
Killed  cultures  may  be  used. 

Eabbits  and  mice  are  the  most  susceptible  ani- 
mals.    The  susceptibility  of  man  is  much  greater. 


Amytoid 
Degeneration. 


JM'ECTIOX  AM)   fMUUMTY 


Susceptibility 
of  Animals. 


Infections 
n  Man. 


Skin. 


The  orgauisins  are  most  virulent  for  rabbits  when 
injected  intra venously,  and  a  variety  of  lesions 
may  result,  as  abscesses  in  various  parts  of  the 
body  (especially  the  kidney,  heart  and  muscles), 
arthritis,  endocarditis,  etc.  They  are  less  patho- 
genic when  injected  into  the  pleural  or  peritoneal 
cavities.  Eabbits  are  rarely  to  be  infected  by  the 
feeding  of  cultures.  In  experimental  infections 
degi'nerations  of  the  axis  cylinders  in  the  white 
and  gray  matter,  and  of  ganglionic  cells,  have  been 
noted.  The  virulence  of  staphylococci  is  subject 
to  great  variations,  and  it  may  be  increased  by 
passage.  In  passing  a  culture  through  the  rabbit 
eight  times,  Lingelsheini  reduced  the  fatal  dose 
for  rabbits  from  5  c.c.  to  1/100  c.c,  but  a  corre- 
sponding increase  in  virulence  for  the  mouse  and 
guinea-pig  did  not  occur.  Virulence  for  animals 
is  not  a  reliable  index  of  virulence  for  man. 

The  staphylococcus  is  the  most  common  pus 
producer  in  man.  The  most  frequent  infections 
are  those  of  the  skin,  the  organisms  gaining  en- 
trance through  the  hair  follicles  rather  than 
through  the  sweat  ducts  (Unna),  resulting  in  such 
conditions  as  acne  pustules,  abscess  of  the  skin 
and  subcutaneous  tissue,  furuncles  and  carbun- 
cles. They  are  found  almost  constantly  in  the 
lesions  of  impetigo  and  often  in  pure  culture. 
They  have  been  much  vaunted  as  a  cause  of 
eczema  and  they  may  be  important  as  a  secondary 
agent  in  this  condition.  The  ordinary  eczema  prob- 
ably is  not  parasitic  in  its  cause,  however  (Sabou- 
raud),  and  ISTeisser  and  Lipstein  dispute  the  claim 
of  Bender  and  others  that  eczema  produced  by 
staphylococcus  fdtrates  is  due  to  products  of  the 
microbe.     This  conclusion  was  Justified,  since  the 


STAPHYLOCOCCUS. 


377 


Mucous 
Surfaces. 


same  results  were  obtained  witli  pure  IjouiUon  of 
similar  alkalinity,  the  property  eould  not  l)e  d(;- 
stroyed  by  heat,  and  antistaphylococcus  serum  was 
not  able  to  prevent  the  dermatitis.  Furuncles  may 
be  produced  by  rubbing  virulent  cultures  into  the 
skin,  and  abscesses  by  the  injection  of  minute 
amounts.  The  staphylococcus  causes  purulent  or 
seropurulent  conjunctivitis  rather  infrequently. 
Primary  infections  of  cavities  which  communicate 
with  the  surface,  as  the  antrum  of  Highmore,  the 
middle  ear,  nose,  bronchi,  lungs  and  tuberculous 
cavities,  are  not  uncommon,  and  mixed  infections 
with  the  staphylococcus  in  these  localities  is  the 
rule,  regardless  of  the  primary  cause.  Infection 
of  the  mucous  surfaces  is  less  common  than  of  the 
skin,  however.  It  rarely  causes  aphthous  inflam- 
mations, anginas,  pneumonia,  enteritis  and  cys- 
titis when  unmixed  with  other  organisms. 

Staphylococcus  septicemia  of  great  virulence  oc-  Septicemia, 
casionally  follows  primary  infection  in  other  parts 
of  the  body,  as  wound  infections,  tonsillitis,  puer- 
peral infection  (rare)  and  the  so-called  malignant 
carbuncles  of  the  uj)per  lip.  In  such  instances  a 
thrombophlebitis  may  be  the  means  by  which  the 
organisms  are  poured  into  the  circulation  in  large 
numbers.  Inflammations  of  the  serous  surfaces, 
as  the  pleura,  peritoneum  and  endocardium,  are 
rarely  primary,  but  follow  systemic  infection;  the 
endocarditis  usually  is  ulcerative  and  leads  to 
metastatic  foci  of  infection.  Staphylococci  have  a 
particular  afiinity  for  the  bony  tissues,  especially 
the  bone  marrow  and  the  periosteum ;  they  are  the 
most  common  agent  in  the  production  of  osteomye- 
litis and  cause  the  so-called  periostitis  albuminosa. 
It  is  thought  that  they  may  persist  in  bone  lesions 


Serous 
Surfaces 
and  Bones. 


37S  /.V/-'7;('77(>\      I  \ /'    nnil  MTV. 

Tor  a  period  of  years  and  later  start  up  a  I'resli 
|)r(H-c'ss.  Tliev  involve  tlie  joints  less  frequently, 
Imt  have  liiH'u  lnund.  iircsiiiiialil y  as  secondary 
ai,^ents.  in  acute  rheumatism,  and  as  tlie  primary 
cause  in  pyemic  abscesses  of  the  joints.  They  are 
found  occasionally  in  abscesses  of  ihc  iiiaininary 
and  parotid  glands,  liver,  lungs,  and  in  [jyorrhea 
MUed   alveolaris  (rare).    The  cultivation  of  staphvlococei 

Infections.  ^  '  '■     • 

in  a  pure  state  from  the  tissues  does  not  of  neces- 
sity indicate  that  they  are  the  essential  organism 
in  the  process  (smallpox,  rlicumatisin.  etc.).  Pre- 
vious infections  by  many  organisms,  and  likewise 
traumas,  predispose  to  localization  of  the  staphy- 
lococcus, and  any  infections  process  in  the  skin  is 
I  lively  to  be  invaded  by  these  organisms  secondarily. 
Leucocytes  lufections  witli  the  staphylococcus  are  charac- 
'il!!i**"I*'   terized  bv  both  local  and  general  leucocvtosis,  the 

Immunity.  ~ 

local  leucocytosis  being  a  part  of  the  suppurative 
process.  As  stated  above,  the  staphylococcus  con- 
tains a  thermostabile  constituent,  Avhich  exerts  a 
])ositive  cliemotatic  effect  on  the  leucocytes.  Al- 
though it  is  possible  to  consider  the  accumulation 
of  the  leucocytes  merely  as  the  expression  of  this 
affinity,  it  has  been  shown  with  sufficient  clearness 
that  polymorphonuclear  leucocytes  are  able  to  in- 
gest living  staphylococci  and  kill  them.*  They 
may  be  found  within  the  leucocytes  in  both  natural 
and  experimental  infections.  When  injected  into 
the  pleural  or  peritoneal  cavity  oL'  the  guinea-pig 
phagocytosis  is  well  begun  within  one-half  bonr 
and  reaches  its  height  in  four  to  five  hours. 
Bactericidal  Experiments  which  were  begun  l)y  van  d<'r  A  elde 
^cocyteJ  a*n"d  in  1894  demonstrate  the  bactericidal  action  of  lou- 


Leucocytic 
Exudates. 


*  Phagoc.vtosis    of    staphylococci    was    first     oljserved    b.v 
Kircli    in    1889. 


<S'7V1  Pll  YhOffOaanH.  379 

cocytic  exudates.  The  action  is  not  so  strong  in 
the  cell-tree  exudate  as  wdien  the  leucocytes  are 
present,  and  when  the  leucocytes  arc  caused  to  dis- 
integrate hy  some  means,  as  by  alternate  freezing 
and  thawing,  trituration,  the  action  of  leucocidin, 
or  treatment  with  distilled  water,  the  bactericidal 
power  of  tlie  fluid  is  increased.  Presumably  the 
leucocytes  discharge  their  bactericidal  contents  into 
the  surrounding  fluid  as  a  result  of  such  inju- 
ries. The  nature  of  the  bactericidal  substance  is 
not  known  exactly;  from  the  fact,  however,  that 
leucocytes  contain  complement  it  has  been  suggest- 
ed that  they  discharge  this  complement  which  then 
acts  with  amboceptors  in  the  serum  in  destroying 
the  organisms.  It  is  possible  that  the  cocci  before 
they  are  taken  up  by  the  leucocytes  have  absorbed 
amboceptors  and  after  their  ingestion  are  suscepti- 
ble to  the  action  of  the  endocellular  complement. 
In  contrast  to  the  distinct  bactericidal  power  of  the 
leucocytes  stands  the  very  low  or  entire  absence  of 
a  similar  action  by  both  normal  and  immune 
serums.  It  would  seem,  then,  that  the  niost  power- 
ful agency  in  natural  resistance  to  invasion  by  the 
staphylococcus  is  represented  in  the  phagocytic 
and  bactericidal  activities  of  the  leucocytes.  Opso-  ' 
nins  are  essential  for  phagocytosis. 

In  1888  Eichet  and  Hericourt  showed  that  it   Active 

•  IT,-  ,1  •    ,  ,.   ,  1  1  1  -J.    Immunization. 

was  possible  to  increase  the  resistance  ot  the  rabbit 
against  the  staphylococcus  b}''  immunization  with 
pure  cultures.* 

One  may  immunize  either  with  living  or  killed 
cultures  or  with  culture  filtrates.     Immunization 

*  Their  experiments  in  protecting  and  curing  other  ani- 
mals with  antistaphylococcus  serum  represent  the  first  at- 
tempt made   in    the  direction  of  passive  immunization. 


380  IXFECTI02s'  AND  IMMUXITY. 

with  the  bacterial  cells  uuist  proceed  slowly  in 
order  to  avoid  killing  the  animals.  When  filtrates 
containing  leucocidin  or  staphylol3^sin  (hemolysin) 
are  used,  antitoxins  for  these  svtbstances  are 
formed.  The  antistaphylolysin  obtained  for  one 
strain  neutralizes  the  hemolysin  of  all  strains. 
The  most  prolonged  immunization  with  bacterial 
cells  causes  no  appreciable  increase  in  bacterioly- 
sins. 

Protection  The  scrum  of  one  who  has  recovered  from  a 
Serums,  staphylococcus  infcctiou,  or  that  of  immunized  an- 
imals, is  protective  for  other  animals;  0.1  to  0.2 
c.c.  of  an  immune  serum  given  subcutaneously 
protected  mice  from  a  fatal  dose  of  cocci  given 
two  hours  later,  whereas  other  mice  were  killed  in 
from.  8  to  12  hours.  When  the  serum  was  given 
24  hours  in  advance  of  the  culture.  0.02  to  0.03 
c.c.  saved  them  (v.  Lingelsheim,  cited  by  Neisser). 
The  results  of  Petersen  and  of  Proscher  were  simi- 
lar. In  spite  of  this  rather  strong  protective  ac- 
tion, immune  serums  have  little  or  no  curative 
power. 

Properties       Xo  clearer  explanation  of  the  action  of  the  im- 

of  Serums.  ,     ^     ,  «>       n     n     i         ii 

mune  serum  is  given  than  that  airorded  by  the 
■  experiments  of  Proscher,  Avho  injected  guinea- 
pigs,  rabbits  and  mice  with  normal  and  immune 
serums  and  followed  this  2-1  hours  later  with  in- 
oculation of  the  cocci  into  the  peritoneal  cavity. 
Thirty  minutes  after  injection  of  the  cocci  the 
exudate  in  all  animals  showed  an  enormous  leuco- 
cytosis.  At  first  they  were  chiefly  mononuclears, 
but  later  gave  place  to  polynuclears.  In  the  ani- 
mals which  had  received  the  immune  serum,  mas- 
sive phagocytosis  had  occurred,  and  in  the  course 
of  an  hour  verv  few  cocci  were  extracellular.     On 


STAPHYLOCOCCUS?.  381 

the  other  liand,  practically  no  phagocytosis  had 
taken  place  in  the  animals  which  had  received  the 
normal  serum  (cited  by  JSTeisser).  Virulent 
staphylococci  were  taken  up  less  readily  than 
avirulent.  Such  results  suggest  that  the  protective 
power  of  the  serum  is  due  to  its  ability  to  stimulate 
phagocytosis,  and  this  in  turn  depends  on  the 
increased  quantity  of  bacteriotropic  substances 
formed  in  the  serum  as  the  result  of  immunization 
(Wright  and  others). 

In  the  hands  of  Wright,  vaccination  with  killed  Vaccination. 
cultures  of  the  staphylococcus  has  been  very  suc- 
cessful in  the  cure  of  obstinate  cases  of  acne,  fur- 
unculosis  and  sycosis  barbae.  Bouillon  cultures 
are  grown  for  three  weeks  and.  then  killed  by  ex- 
posure to  a  temperature  of  60°  C.  for  an  hour.  In 
order  to  control  dosage,  the  vaccine  is  standardized 
by  estimating  the  number  of  bacilli  in  each  cubic 
centimeter.  This  is  done  by  mixing  equal  quanti- 
ties of  the  vaccine  with  normal  blood,  and,  after 
staining  a  preparation  on  a  slide,  determining  the 
ratio  of  cocci  to  erythrocytes.  There  being  about 
5,000,000  erythrocytes  to  the  cubic  millimeter  In 
normal  blood,  the  number  of  cocci  is  readily  reck- 
oned from  the  ratio  which  was  found.  From 
2,500  millions  to  7,500  millions  of  cocci  may  be 
given  in  an  injection.  The  quantity  to  be  used  is 
determined  by  the  effect  which  an  injection  has  on 
the  opsonic  content  of  the  patient's  serum.  If  a 
suitable  dose  has  been  given,  there  occurs  a  short 
negative  phase  in  which  the  opsonins  are  decreased 
in  quantity,  and  this  is  followed  by  a  rather  pro- 
longed positive  phase  when  they  undergo  an  in- 
crease. If  too  large  a  dose  is  given,  the  negative 
phase  is  exaggerated  and  prolonged.     In  many  in- 


382  !Xri:CTl(>\    A\l>   l]nil  MTV. 

"Opsonic  stances  it  has  been  noted  that  iiuprovoinent  and 
'"****■'  recovery  go  liand  in  liand  witli  an  ineroase  in  the 
opsonins.  The  quantity  of  opsonins  present  in  a 
serum  is  expressed  by  an  "opsonic  index."* 
Agglutination.  q^hp  normal  scrums  of  man  and  many  animals 
nniy  agglutinate  the  staphylococcns.  l)ut  witli  no 
constancy.  In  one  instance  human  serum  ag- 
glutinated in  a  dilution  of  1-100  (Kraus  and 
Low),  and  normal  goat  serum  in  a  dilution  of 
1-50  to  1-100  (Amberger,  cited  by  Xeisser).  The 
serums  from  cases  of  staphylococcus  infection 
(e.  g.,  osteomyelitis)  and  of  highly  immunized  an- 
imals undergo  an  increase  in  the  quantity  of  ag- 
glutinins. The  agglutination  usually  is  strongest 
for  the  homologous  strain,  and  if  other  strains  are 
agglutinated  equally  it  signifies  a  close  relation- 
ship to  the  homologous  strain. 

From  the  fact  that  only  pathogenic  strains  pro- 
duce    liemolysin     and     leucocidin,     Neisser     and 

*  To  obtain  the  opsonic  index  human  leucocytes,  oli- 
tained  from  deflhrinated  blood,  are  washed  free  of  serum, 
and  equal  parts  are  added  to  two  e(|ual  jiortions  of  an  emul- 
sion of  the  staphylococcus.  One  portion  of  the  emulsion  has 
previously  been  treated  with  the  serum  of  the  patient  for 
about  twenty  minutes,  and  the  other  portion  with  normal 
human  serum.  The  opsonins  of  the  two  serums  combine 
with  the  cocci,  rendering  them  susceptible  to  phagocytosis 
(sensitization).  After  the  leucocytes  have  been  in  contact 
with  the  sensitized  cocci  for  fifteen  to  thirty  minutes,  films 
of  the  two  mixtures  are  stained  with  the  Romanowsky  or 
a  similar  stain,  which  colors  both  the  cells  and  the  cocci. 
The  average  number  of  cocci  in  say  fifty  leucocytes  on  each 
slide  is  determined.  The  average  phagocytosis  in  the  pa- 
tient's serum  divided  by  that  in  the  normal  serum  gives  the 
opsonic  index.  For  example,  if  the  former  showed  an 
average  of  10  cocci  to  each  leucocyte  and  the  latter  an 
average  of  5,  the  index  is  2.  The  degree  to  which  the  op- 
sonic index  can  be  raised  by  the  immunization  varies.  In 
one  instance  it  was  increased  from  .S  to  I.Ci  :  in  another  case 
which  reacted  less  vigorously  it  was  raised  from  .87  to  .95. 


MI(JU()(HW(J(JS   (JATAURIIMjIH.  .'i8:j 

Wechsberg-  considered  them  specifically  difteront 
from  non-pat] logenic  strains.  This  view  is  borne 
out  by  the  results  obtained  with  the  agglutination 
test.  Serums  obtained  by  immunization  with 
pathogenic  strains  have  a  much  higher  aggluti- 
nating power  for  these  strains  than  for  non-patho- 
genic varieties,  and  the  converse  is  also  true.  There 
are,  however,  many  variations  in  the  agglutinabil- 
ity  of  the  members  in  each  group,  a  fact  which  in- 
dicates variations  in  the  receptor  complex  of  the 
different  strains.  It  has  been  suggested  that  a 
polyvalent  serum  obtained  by  immunization  with 
a  sufficient  variety  of  pathogenic  strains  will  be 
efficient  in  difEerentiating  the  latter  from  non- 
pathogenic varieties  by  means  of  the  agglutina- 
tion test. 

Wright,  noting  an  increase  in  the  agglutinating 
power  when  patients  are  treated  by  his  method, 
considers  that  this  increase  is  an  index  of  the  im- 
munity which  is  established. 

IV.    MICROCOCCUS    CATARRHALIS. 

For  some  years  diplococci  resembling  the  gono- 
coccus  and  the  meningococcus  morphologically  and 
in  staining  reactions  have  been  found  in  the  spu- 
tum by  a  number  of  observers,  and  to  this  coccus 
Pfeiffer  gave  the  name  of  Micrococcus  catarrlialis. 
It  is  frequently  found  in  the  respiratory  passages 
in  influenza-like  infections  and  other  inflamma- 
tory conditions,  and  occasionally  in  lobular  pneu- 
monia. It  may  be  associated  with  the  influenza 
bacillus  or  the  pneumococcus.  Among  140  cases 
of  diseases  of  the  respiratory  passages  Gohn  and  H. 
Pfeiffer  found  it  eighty-one  times,  and  M.  ISTeisser 
demonstrated    it    in    sixteen   cases    of    whooping- 


384  lyFECTION  AND  IMMUNITY. 

.  lougli.  in  one  ol'  measles  and  scarlet  fever,  and  in 
two  of  diplitlieria.  It  loses  signiiicance  in  relation 
to  these  diseases,  however,  since  Jiindell  found  it 
frequently  in  the  mucus  of  the  normal  trachea, 
and  Weichselbaum  cultivated  it  frequentl}^  from 
the  healthy  nasal  fossse.  According  to  Gohn, 
Pfeiffer  and  Sederl,  "The  Micrococcus  catarrhaUs, 
■\^^thout  the  association  of  other  microbes,  is  able 
to  cause  bronchitis  and  pneumonia  with  the  clini- 
cal type  of  pneumonia  due  to  the  pneumococcus. 
The  symptoms  caused  by  the  Micrococcus  catarrh- 
alt^  do  not  form  a  clinical  type.  They  resemble 
infections  by  the  pneumococcus  or  the  bacillus  of 
Pfeiffer  (Influenza)"  (cited  by  Bezancon  and  de 
Jong).  Others  are  not  so  positive  concerning  the 
pathogenic  properties  of  the  organism.  Its  etio- 
logic  role  is  not  yet  well  established.  It  has  little 
pathogenicity  for  animals,  although  peritoneal  and 
pleural  infection  is  possible  in  guinea-pigs. 

It  differs  from  the  gonococcus  and  meningococ- 
cus in  certain  cultural  characters. 

Y.    GONORKHEA  AND  OTHER  INFECTIONS   WITH  THE 
GONOCOCCUS. 

Tha  A.  Neisser  discovered  the  gonococcus  in  1879, 
Gonococcus.  cultivated  it  in  1884,  and  demonstrated  its  specific 
relation  to  gonorrhea  by  the  inoculation  of  pure 
cultures  into  the  human  urethra.  It  is  a  diplo- 
coccus,  young  pairs  having  a  figure-of-eight  con- 
tour, whereas  older  pairs  show  a  typical  biscuit 
or  coffee-bean  shape.  The  organism  is  non-motile, 
has  no  flagella  and  forms  no  spores.  It  can  be 
cultivated  only  on  media  which  contain  serum, 
ascitic  or  a  similar  fluid.  Its  failure  to  stain  by 
Gram's  method  is  of  great  diagnostic  importance 


GOWOCOCCUS. 


385 


in  the  examination  of  urethral  discharges;  other 
organisms  resembling  the  gonococcus  are  found  in 
the  urethra  and  vagina  with  great  rarity.  The 
reaction  loses  its  differential  value  in  the  examina- 
tion of  secretions  of  the  nose,  mouth,  and,  to  some 
extent,  of  the  conjunctiva,  where  the  meningococ- 
cus and  the  Micrococcus  catarrhaUs  may  be  en- 
countered. 

In  the  purulent  stage  of  a  gonorrheal  infection  phagocytosis, 
the  cocci  are  found  almost  entirely  within  the  leu- 
cocytes, whereas  in  earlier  stages, .  when  the  dis- 
charge is  slight  and  of  a  mucous  character,  and 
also  during  convalescence,  when  the  secretion 
again  becomes  mucous,  they  are  largely  extracel- 
lular. They  are  never  within  the  nuclei.  The 
process  is  one  of  active  phagocytosis  in  which  the 
cocci  play  a  passive  role.  They  occur  not  only  on 
the  surface  of  the  epithelium,  but  penetrate  be- 
tween and  beneath  the  epithelial  cells,  and  even 
into  the  adjacent  connective  tissue. 

In  culture  media  growth  is  slow  and  scant,  and  Cuitivatjon 
cultures  rarely  live  longer  than  one  or  two  weeks, 
unless  they  are  transplanted  to  suitable  fresh  media. 
On  the  latter  they  may  be  carried  through  many 
generations  without  losing  their  virulence.  When 
dried  they  die  very  quickly,  but  may  live  for  some 
hours  on  linen  (towels)  or  the  skin,  and  for 
twenty-four  hours  in  warm  water.  They  are  very 
susceptible  to  temperatures  above  42°  to  43°  C. 
and  show  very  little  resistance  to  antiseptics,  par- 
ticularly the  silver  salts. 

The  gonococcus  secretes  no  soluble  toxin,  but 
contains  an  endotoxin  or  toxic  "protein^'  which 
causes  local  and  general  symptoms  in  both  man 
and  animals.    Dead  cultures  produce  an  inflamma- 


and  Resistance. 


Toxicity  and 
Virulence. 


Susceptible 
Tissues. 


380  l\ri:CTf<)\   A\l>   IMMIXITY. 

tor}'  exudate  in  the  peritoneal  cavity  of  guinea- 
pigs  and  mice,  resulting  in  death  if  the  dose  is 
sufficiently  large,  and  when  injected  into  the 
urethra  of  man  a  temporary  inflammation  results. 
An  actual  infection  of  any  sort  can  not  be  pro- 
duced in  animals;  the  cocci  are  killed  without  be- 
ing permitted  to  proliferate.  The  endotoxin  (gon- 
otoxin)  is  fairly  resistant  to  heat,  being  destroyed 
only  after  prolonged  exposure  to  a  temperature  of 
100°  C. 

In  man  the  mucous  membranes  and  endothelial 
.surfaces  are  more  susceptible  to  infection  than 
other  tissues.  The  urethra  of  male  and  female  at 
all  ages,  the  conjunctiva  in  the  new-born,  the 
vagina,  nterus  and  tubes  are  probably  the  most 
susceptible.  Less  susceptible  are  the  vagina  in 
older  women,  especially  those  who  have  borne  chil- 
dren; the  bladder,  and  in  adults  the  conjunctiva. 
It  is  remarkable  that  there  are  so  few  cases  of 
gonorrlieal  ophthalmia  in  adults,  considering  the 
opportunities  for  infection.  Infection  of  the 
mouth,  nose  and  tear  sacs  is  extremely  rare.  Ex- 
tension from  the  urethra  to  adjacent  structures 
takes  place  either  by  way  of  the  surfaces,  as  in 
involvement  of  the  prostate,  epididymis,  glands  of 
Bartholin,  uterus,  tubes,  ovaries,  peritoneum,  blad- 
der and  kidneys,  or  by  way  of  the  lymphatics  as  in 
infections  of  the  periurethral  tissue  or  cellular  tis- 
sue of  the  pelvis.  Usually  infections  of  the  bladder 
and  kidney,  and  not  infrequently  of  the  prostate. 
Fallopian  tubes  and  j^elvic  tissue  are  of  a  mixed 
character  (staphylococcus,  streptococcus),  but  not 
necessarily  so.  Arthritis,  tendovaginitis,  endocar- 
ditis, which  usually  is  vegetative  but  may  be  ulcer- 
ative, are  the  more  common  metastatic  complica- 


(joxoaoccuH. 


387 


tions.  Less  frequent  are  pericarditis,  pleuritis, 
subcutaneous  abscesses  and  iritis.  As  to  whether 
the  cutaneous  phenomena  sometimes  seen  are  due 
to  metastases  or  are  of  purely  toxic  origin  seems  to 
be  undetermined.  The  blood  stream  may  be  in- 
fected by  way  of  the  lymphatics  or  local  blood 
vessels  (gonorrheal  thrombosis). 

The  influence  of  the  enormous  phagocytosis  of 
the  cocci  on  the  course  of  gonorrhea  is  unknown. 
Since  the  ingested  cocci  usually  have  a  typical 
form  and  stain  well,  it  would  seem  that  they  resist 
the  action  of  the  leucocytic  ferments.  Likewise 
the  nuclei  of  the  leucocytes  usually  stain  well, 
hence  there  is  no  evidence  of  a  marked  toxicity 
of  the  cocci  for  these  cells.  The  mechanical  im- 
prisonment of  the  organisms  by  the  leucocytes 
may  be  of  influence  in  localizing  the  infection. 

During  the  course  of  gonorrhea  "there  takes  urethral 
place  a  pronounced  metaplasia  of  the  epithelium 
in  which  the  cylindrical  cells  are  changed  into  a 
more  cuboidal  and  even  pavement  form."  Follow- 
ing this  change  the  gonococci  are  limited  to  the 
surface  of  the  altered  epithelium  and  penetrate 
more  deeply  only  in  the  vicinity  of  the  glands  and 
crypts.  "Eventually  the  gonorrheal  process  is 
limited  to  such  isolated  points  and  the  gonorrhea 
thereby  enters  into  a  chronic  stage"  (observations 
of  Finger,  cited  by  Neisser  and  Scholtz). 

The  conditions  which  cause  the  subsidence  of  chronic 
acute  gonorrhea  and  allow  it  to  persist  as  a  chronic 
infection  have  been  the  subject  of  much  specula- 
tion, unproductive  for  the  most  part.  It  is  not 
due  to  a  decrease  in  the  virulence  of  the  cocci 
since  their  original  infectiousness  is  retained  for 
others :  nor  does  the  local  resistance  of  the  mucous 


388 


IM'KCTIOX  A.\n   IM.MUXITY. 


Immunity. 


uiouibraue  reach  a  high  point,  since  reinfection, 
or  better  "'superinfection"  is  possible  at  any  time. 
A  man  suffering  from  clironic  gonorrhea  and 
liaving  infected  his  M'ife,  may  again  be  infected 
by  his  wife  when  the  gonorrhea  of  the  latter  has 
become  subacute  or  chronic.  It  has  been  suggested 
that  the  condition  in  chronic  gonorrhea  may  be 
one  of  "mutual  habituation  between  the  mucous 
membrane  and  the  gonococcus,"  i.  e.,  a  habituation 
between  this  particular  mucous  membrane  and 
this  particular  gonococcus.  Because  of  prolonged 
existence  under  unvarying  conditions,  the  growth 
energy  of  the  organism  may  have  become  less, 
whereas,  if  it  is  placed  in  a  slightly  different  me- 
dium (transference  to  another  individual),  its 
growth  energy  (ability  to  proliferate),  becomes 
augmented,  and  reinfection  of  the  original  host 
Avith  the  same  strain  becomes  possible. 

It  has  often  been  noted  that  subsequent  attacks 
run  a  milder  course  than  the  primary  infection, 
but  susceptibility  is  always  present. 

Mendez,  Calvino,  and  also  de  Christmas  have 
immunized  with  the  coccus  or  toxic  substances 
prepared  from  it.  By  growing  the  organism  in 
serum  bouillon  de  Christmas  prepared  a  toxin, 
the  toxicity  of  which  was  tested  by  intracerebral 
injections  in  the  guinea-pig.  Immunization  of 
the  guinea-pig  resulted  in  a  serum  with  antitoxic 
properties.  Corroborative  work  has  not  been  pub- 
lished. 


VI.    EPIDEMIC    CEREBROSPINAL    MENINGITIS. 

^Cau^^na       -^cute  inflammation  of  the  meninges  may  be 
Meningitis,  caused  by  a  number  of  micro-organisms:     Micro- 
coccus meningitidis,   also  called   the  Diplococcus 


MENINOOCOCGUS.  389 

intracellular  is  meningitidis,  or  briefl_y  the  men- 
ingococcus; Diplococcus  pneumonia;;  Streptococ- 
cus pyogenes;  Staphylococcus  pyogenes;  Bacillus 
influenza;  Bacillus  pneumoniw ;  Bacillus  iypli,o- 
sus;  Bacillus  coli  communis;  Bacillus  mallei;  Ba- 
cillus pestis.  The  first  two  of  this  number,  the 
meningococcus  and  the  pneumococcus,  in  addition 
to  causing  sporadic  cases,  also  produce  more  or 
less  extensive  epidemics  of  so-called  primary  men- 
ingitis. That  the  pneumococcus  may  also  cause 
meningitis  secondary  to  pneumococcus  infections 
in  other  parts  of  the  body  has  been  mentioned. 
Also  the  meningitis  caused  by  the  other  pyogenic 
cocci  usually  is  secondary  to  some  other  suppura- 
tive focus,  often  the  middle  ear;  that  caused  by 
the  organisms  of  typhoid,  glanders,  plague  and 
influenza  occurs  during  the  course  of  the  diseases 
•caused  by  the  corresponding  micro-organisms. 

Previous  to  1887  diplococci  resembling  the  pneu-   Micrococcus 

„^       -,  -,  .  Meningitidis. 

mococcus  had  been  found  m  the  exudate  m  cases 
of  cerebrospinal  meningitis  by  Foa  and  Bordoni- 
Uffreduzzi,  by  Fraenkel  and  others.  Weichsel- 
baum  made  similar  observations  during  the  same 
y^ear,  and  in  addition  described  six  cases  in  which 
a  diplococcus  of  another  nature  was  present  in 
pure  cultures.  To  the  latter  he  gave  the  name  of 
Diplococcus  intracellularis  meningitidis.  Exten- 
sive observations  by  others,  both  in  Europe  and 
America  (Councilman,  Mallory  and  Wright,  and 
others),  revealed  the  presence  of  the  last-named 
organism  in  many  instances,  and  showed  that  it  is 
the  most  common  cause  of  epidemic  cerebrospinal 
meningitis. 

The    meningococcus    resembles    the    gonococcus 
closely  in  that  it  is  usually  found  in  biscuit-shaped 


390 


LM'KrTlOX   A\D   IMMIMTY. 


Resistance. 


Virulence; 
Endotoxin. 


Infection 
Atria, 


pairs,  nearly  always  witliin  pus  cells,  and  does  not 
stain  by  Gram's  method  (Weichsclbaum).  It  is 
properly  to  be  called  a  micrococcus  since  it  divides 
in  two  transverse  directions  (Albrccht  and  Gohn)  ; 
tetrads,  small  groups  and  short  chains  are  some- 
times seen.  However,  it  forms  no  striking  chains, 
is  non-motile  and  produces  no  spores.  Growth 
m«i.y  be  obtained  on  some  of  the  ordinary  media 
(glycerin  agar),  in  which  the  organism  differs 
from  the  gonococcus,  but  a  medium  which  contains 
blood  or  serum  is  much  more  favorable.  It  is  an 
obligate  aerobe,  grows  best  at  the  body  tempera- 
ture and  virulence  is  soon  lost  under  artificial 
conditions. 

It  produces  a  membrane  on  meat  broth  with 
clouding  of  the  medium.  Viability  is  retained 
only  for  a  few  days  at  room  temperature.  When 
dried  on  paper  and  exposed  to  the  sunlight  it  lives 
no  longer  than  twenty-four  hours,  in  a  dark  room 
seventy-two  hours  (Councilman.  ]\ralIory  and 
Wright).  It  is  killed  by  a  temperature  of  65°  C. 
for  thirty  minutes  (Albrecht  and  Gohn). 

The  meningococcus  has  little  virulence  for  ani- 
mals. When  injected  in  sufficient  quantity  into 
the  peritoneal  or  pleural  cavity  of  white  mice 
death  results  in  from  twenty-four  to  forty-eight 
hours,  but  not  when  given  subcutaneously.  Men- 
ingitis may  be  produced  by  subdural  injections, 
but  the  disease  does  not  resemble  the  epidemic 
meningitis  of  man.  So  far  as  is  known  at  the 
present  time  the  organism  does  not  produce  a 
soluble  toxin,  but  possesses  rather  an  endotoxin. 

Although  the  disease  is  usually  spoken  of  as  a 
primary  meningitis,  there  is  reason  to  believe  that 
it  is  secondary  to  an  acute  rhinitis  or  acute  in- 


MENINGOCOCCUS.  391 

flammation  of  the  accessory  sinuses  or  middle  ear, 
in  many  instances.  From  these  places  the  coccus 
may  readily  reach  the  meninges  by  way  of  the 
lymphatic  channels.  It  has  been  found  repeatedly 
in  the  noses  of  those  who  were  associated  with 
cases  of  the  disease;  in  such  cases  an  acute  rhi- 
nitis may  be  present  without  the  subsequent  de- 
velopment of  meningitis.  Clinical  histories  show 
that  the  infection  commonly  is  preceded  by 
acute  rhinitis.  The  inflammation  in  the  meninges 
is  always  cerebrospinal  in  its  distribution  and 
is  characterized  by  a  purulent  or  fibrino-purulent 
exudate  in  which  the  diplococci  are  present  in 
varying  quantities.  Diagnosis  may  often  be  estab- 
lished clinically  by  the  microscopic  or  cultural 
examination  of  the  cerebrospinal  fluid  which  is 
removed  by  lumbar  puncture. 

Acute  encephalitis,  acute  bronchitis,  lobar  pneu-  complications 
monia  and  acute  arthritis  have  been  observed  as  f„"fertions, 
complications,  in  which  organisms  resembling  the 
meningococcus'  have  been  found  in  a  number  of 
instances.  An  accompanying  bronchitis,  lobar  or 
lobular  pneumonia  may  be  caused  by  mixed  infec- 
tion with  other  organisms  (pneumococcus,  strepto- 
coccus, staphylococcus).  Since  it  would  be  diffi- 
cult to  explain  some  of  these  complications  except 
on  the  basis  of  metastasis,  it  seems  very  probable 
that  the  organism  reaches  the  blood  stream.  Micro- 
cocci resembling  the  meningococcus  have  been 
found  in  acute  bronchitis,  rhinitis,  lobular  pneu- 
monia and  conjunctivitis,  in  the  absence  of  cere- 
bral involvement,  and  it  is  possible  that  it  may  be 
the  cause  of  independent  inflammations  in  these 
tissues.  Weichselbaum,  however,  is  inclined  to 
doubt   the  identity'  of   such   organisms   with   the 


392 


IXFECTIOX  AND  IMMUXITY. 


Transmission 
and  Contag- 
iousness. 


Susceptibility 
and  Immunity. 


meningococcus.  Particular!}'  in  cases  of  bronchi- 
tis and  lobular  pneumonia  the  coccus  may  be  con- 
fused with  the  Micrococcus  catarrhalis  of  Pfeitl'er, 
with  which  it  is  identical  morphologically. 

The  extent  to  "vvliich  the  meningococcus  is  a 
normal  iuhal)itant  of  the  nasal  mucous  membrane 
is  unknown. 

Since  the  organism  seems  to  be  excreted  chiefly 
or  only  with  the  nasal  discharges,  the  latter  prob- 
ably are  important  for  transmission  of  the  infec- 
tion. Because  of  the  low  resistance  of  the  organ- 
ism to  desiccation  and  light,  transmission  prob- 
ably is  a  fairly  direct  one.  This  is  suggested  also 
by  the  occasional  occurrence  of  epidemics  in  insti- 
tutions. Contagiousness  is  of  a  rather  low  order ; 
this  is  indicated  by  the  distribution  of  the  111 
cases  observed  by  Councilman,  j\[allory  and 
Wright  in  Boston^  the  city  being  somewhat  dif- 
fusely infected  with  very  little  tendency  of  the  dis- 
ease to  occur  in  groups  of  individuals  or  in  several 
members  of  a  family. 

The  desirability  of  avoiding  contact  with  the 
infected  is  evident;  special  prophylactic  meas- 
ures are  not  known.  In  the  presence  of  an  epi- 
demic the  treatment  of  rhinitis  with  local  antisep- 
tics would  suggest  itself. 

Children  and  young  people  are  particularly  su^;- 
ccptible  to  both  epidemic  and  sporadic  infections 
Avitli  the  meningococcus.  Exposure  incident  to  the 
cold  and  variable  weather  of  the  winter  and  spring, 
in  which  seasons  the  disease  prevails,  may  be  in- 
fluential in  lowering  resistance.  Second  attacks 
are  rare.  Councilman,  Mallory  and  Wright  col- 
lecting only  five  such  examples  from  the  literature. 
Lipierre   immunized    animals   with   cultures    and 


m  FLU  EN  Z  A.  393 

with  a  toxin,  the  hitter  being  a  glycerin  extract  of 
old  cultures.  Their  resistance  to  infection  was 
said  to  be  increased,  and  the  serum  of  highly  im- 
munized animals  was  antitoxic,  preventive  and 
curative  for  other  animals.  Corroborative  work 
is  lacking.  According  to  Davisj  the  serum  in 
cases  of  epidemic  meningitis  shows  an  increased 
bactericidal  power  for  the  coccus  on  the  thirteenth 
day  of  the  disease;  the  agglutinins  which  develop 
probably  persist  for  some  time,  but  are  little  above 
the  normal  after  two  and  one-half  years.^  Fairly 
strong  agglutinins  may  be  obtained  by  the  im- 
munization of  rabbits  (Jager  and  Albrecht  and 
Gohn). 

VII.    INFLUENZA. 

Influenza  occurs  sporadically  and  in  epidemics 
of  greater  or  less  proportions.  Its  extreme  con- 
tagiousness is  shown  by  the  striking  rapidity  with 
which  it  spread  over  the  whole  civilized  world  in 
the  epidemic  of  1889  and  1890,  leaving  behind  it 

1.  The  conclusions  of  Dr.  Davis  are  as  follows  :  In  five 
leases  of  epidemic  cerebrospinal  meningitis,  the  meniugococcus 
(Weichselbaum  type),  was  obtained  in  every  case  from  the 
cerebrospinal  fluid,  and  in  one  case  from  the  nose  and 
sputum  by  cultures.  In  the  other  four  cases  Gram-negative 
diplococci  suggestive  of  either  meningococcus  or  Micrococcus 
catarrhalis  were  seen  in  smears,  but  were  not  recovered  in 
cultures.  Agglutination  of  meningococcus  by  the  serum  of 
patients  with  meningitis  occurs  in  a  dilution  of  1-5  or  higher. 
The  meningococcus  grows  in  some  deflbrinated  normal  bloods, 
but  not  in  others,  there  being  thus  an  interesting  individual 
variation.  In  the  blood  of  three  meningitis  cases  it  did  not 
grow.  Normal  human  serum  is  distinctly  bactericidal  toward 
the  meningococcus.  This  property  is  increased  in  sera  of 
meningitis  cases,  and  is  diminished,  but  not  entirely  de- 
stroyed by  heating  to  60  C.  for  thirty  minutes.  Cerebro- 
spinal fluid  acts  in  much  the  same  way  as  heated  serum. 
The  opsonin  content  of  the  blood  does  not  appear  to  be 
altered  during  the  course  of'  epidemic  meningitis.  Normal 
cerebrospinal  fluid  does  not  contain  opsonin  for  meningococci. 
— Jour,   of  Infectious  Diseases,  1905,  vol.   ii. 


394 


IXFECTIOy  AND  IMMUNITY. 


Bacillus 
Influenz*. 


Symbiosis. 


Pseudo- 
Influenza 
Bacilli. 


a  trail  oi:  lesser  epidemics  which  have  prevailed  up 
to  tlie  present  time. 

During  the  epidemic  just  cited  a  number  of  or- 
ganisms were  erroneously  described  as  the  cause  of 
the  disease.  In  1892,  however,  Pfeiffer  discovered 
a  minute  bacillus  which  he  found  constantly  and 
in  large  numbers  in  the  sputum  of  influenza  pa- 
tients only.  Tlic  observations  of  Pfeiffer  have 
been  confirmed  by  a  large  number  of  investigators, 
and  the  organism,  Bacillus  influenza',  is  now  ac- 
cepted as  the  cause  of  the  disease.  It  is  one  of  the 
smallest  of  bacteria  (0.2  or  0.3  by  0.5  microns),  is 
non-motile  and  forms  no  spores.  A  medium  con- 
taining blood  or  hemoglobin  is  essential  for  its 
artificial  cultivation,  and  even  under  the  best  con- 
ditions it  grows  meagerly  and  slowly.  A  number 
of  bloods,  but  particularly  those  of  man  and  the 
dove,  favor  its  growth.  It  is  a  strong  aerobe.  The 
organism  is  best  stained  by  a  dilute  solution  of 
carbol  fuchsin  (1  to  10),  and,  like  the  plague 
bacillus,  exhibits  polar  staining,  i.  e.,  the  ends 
stain  more  deeply  than  the  central  portion. 

^\lien  the  staphylococcus  and  some  other  organ- 
isms are  grown  in  mixed  culture  with  the  influ- 
enza bacillus,  the  latter  is  stimulated  to  a  more 
vigorous  growth.  According  to  Jacobsohn,  killed 
cultures  of  the  streptococcus  greatly  increase  the 
virulence  of  the  influenza  bacillus  when  the  mix- 
ture is  injected  into  animals. 

Pfeiffer  designates  as  pseudoinfluenza  bacilli  a 
number  of  influenza-like  organisms  w^hich  have 
been  found  in  man  and  animals.  They  have  the 
morphology  of  the  influenza  bacillus,  are  a  little 
larger,  and  also  prefer  a  medium  which  contains 
hemoglobin,  but  since  some  of  them  occur  in  ani- 


INFLUENZA.  395 

mals  which  are  known  not  to  be  susceptible  to  in- 
fluenza, it  is  concluded  that  they  can  not  be  identi- 
cal with  the  influenza  bacillus.  The  influenza-like 
bacillus  which  Jochmann  and  Krause  consider  as 
the  cause  of  whooping-cough,  may  be  mentioned 
in  this  connection. 

The  resistance  of  the  bacillus  to   desiccation,  Resistance 

ane  Virulence. 

sunlight  and  unfavorable  temperatures  is  very  low. 
It  dies  in  from  twenty-four  to  thirty-six  hours  at 
room  temperature,  when  contained  in  sputum,  and 
lives  for  about  thirty-two  hours  in  hydrant  water 
(Pfeifler).  It  is  not  highly  virulent  for  experi- 
ment animals,  although  a  condition  said  to  resem- 
ble influenza  has  been  produced  in  monkeys  b}' 
placing  pure  cultures  on  the  nasal  mucous  mem- 
brane. Fatal  infections  may  be  produced  by  intra- 
venous inoculation  of  the  bacillus  into  monkeys 
and  rabbits,  and  killed  cultures  produce  a  fatal 
intoxication  in  rabbits.  Virulent  cultures  in  suffi- 
cient quantity  produce  fatal  peritonitis  in  guinea- 
pigs.  Since  the  bacilli  seem"  not  to  proliferate 
when  fatal  quantities  are  injected  intravenously 
into  rabbits,  and  since  fatal  intoxication,  without 
the  occurrence  of  bacteriemia,  may  take  place 
when  a  tracheal  infection  is  induced  in  the  ape 
(Pfeiffer),  it  is  concluded  that  the  toxic  phenom- 
ena of  influenza  are  due  to  the  absorption  of  bac- 
terial toxins  from  the  mucous  surfaces.  A  soluble 
toxin  has  not  been  obtained  in  culture  media.  The 
organism  is  a  facultative  pus  producer. 

So  far  as  is  known  the  influenza  bacillus  is  ex-  Distribution 
creted  only  with  the  secretions  of  infected  surfaces, 
i.   e.,   from  the  upper  respiratory  passages,   con- 
junctiva,  ear,   etc.     The  belief,  commonly  held, 
that  the  influenza  bacillus  does  not  enter  the  cir- 


396  I M' EC  T I  OX  AND  IMMIWITY. 

culation  probably  is  erroneous.  That  metastatic  * 
infection  is  possible,  by  way  of  the  lymph  or  blood 
channels,  is  shown  by  the  occurrence  of  influenza 
meningitis,  and,  rarely,  of  influenza  peritonitis 
(Hill  and  Fisch).  According  to  Jehle,  the  influ- 
enza bacillus  invades  the  blood  very  frequently  in 
some  of  the  acute  exanthemata.  It  was  found  in 
the  blood  in  22  out  of  48  cases  of  scarlet  fever,  in 
15  of  23  cases  of  measles,  and  in  5  of  9  cases  of 
varicella  (cited  by  Hektoen).  Hence,  these  dis- 
eases would  seem  to  create  conditions  favorable  for 
invasion  by  this  bacillus.  When  the  bacilli  reach 
the  blood  they  probably  are  killed  quickly.  It  is 
probable  that  the  ordinary  nervous  phenomena  of 
the  disease  are  due  to  intoxication  rather  than  to 
actual  infection  of  the  nervous  structures.  As  to 
whether  the  symptoms  of  so-called  intestinal  in- 
fluenza are  due  to  an  invasion  of  the  intestines 
by  the  bacilli  or  to  a  specialized  action  of  circu- 
lating toxin  seems  not  to  have  been  definitely  set- 
tled. There  certainly  is  abundant  opportunity  for 
infection  of  the  intestines  in  cases  of  bronchial 
influenza.  In  the  bronchitis  of  influenza  the  or- 
ganisms are  found  in  large  numbers  in  the  smaller 
Ijronchial  tubes,  both  free  and  within  leucocytes, 
hence,  in  searching  for  the  bacilli  clinically  it 
should  be  certain  that  the  sputum  examined  repre- 
sents the  bronchial  exudate.  In  influenza  pneu- 
monia, which  usually  is  of  the  lobular  type,  the 
bacilli,  mixed  with  pus  cells  and  contained  in 
them,  are  found  in  large  numbers  in  the  alveoli. 
Pure  cultures  of  the  bacillus  have  been  obtained 
from  cases  of  .conjunctivitis,  and  they  occur  not 
infrequently  in  middle-ear  complications  which 
develop  during  tlic  course  of  the  disease.     Influ- 


Infections. 


INFLUENZA.  397 

cnza  conjunctivitis  sometimes  occurs  in  epidemic 
form,  particularly  in  institutions  and  schools. 

Pneumonic  foci  which  develop  during  influenza  Mi^ed 
frequently  show  the  pneumococcus,  and  sometimes 
the  streptococcus  or  the  bacillus  of  Friedlander  in 
addition  to  the  influenza  bacillus,  and  similar 
mixed  infections  occur  in  pleurisy  and  in  middle- 
ear  disease.  Influenza  may  be  superimposed  on 
other  infections;  individuals  suffering  from  pul- 
monary tuberculosis  are  particularly  susceptible  to 
influenza,  and  in  them  the  prognosis  is  unfavor- 
able. 

The  disease  is  transmitted  directly  from  man  to  Transmis- 

n       1  •    n        •      •  11  p    •         siofit  Infec- 

man  and,  chieny,  it  is  supposed,  by  means  of  m-  tion  Atria 
fected  droplets  of  sputum  which  are  expelled  in  yiaxis. 
coughing  and  sneezing.  Obviously  kissing  affords 
opportunity  for  infection.  Infection  by  indirect 
contact  is  of  less  importance  because  of  the  rapid 
death  of  the  bacillus  after  it  leaves  the  body,  but 
living  germs  may  well  be  disseminated  by  soiled 
handkerchiefs  or  other  contaminated  linen.  Dust 
infection  possibly  is  of  minor  consequence.  Chronic 
influenza  in  which  the  bacilli  may  persist  in  the 
bronchi  for  weeks,  and  cause  recurrent  acute  at- 
tacks, is  of  importance  for  the  maintenance  of  an 
epidemic.  In  tuberculous  cavities  the  bacilli  may 
flourish  for  long  periods. 

Primary  infection  takes  place  in  the  upper  res- 
piratory passages,  and  the  disease  extends  readily 
from  one  surface  to  another,  as  from  the  nose  to 
the  pulmonary  tissue.  Infection  of  the  ear  usually 
is  a  complication  of  pharyngeal  or  pulmonary  in- 
fection. Occasionally  an  influenza  conjunctivitis 
is  found  without  other  localization.  "Primarj** 
infection  of  other  organs,  as  the  brain  and  perito- 


398  i\ri:cri(i\    \\i>  immcmty. 

neuni,  are  inetastalic-,  altlioiiuli  tlic  urigiiuil  focus 
or  atrium  may  not  be  observed. 

Little  or  nothing  can  be  done  in  the  way  of 
general  prophylaxis.  Washing  of  the  nose  and 
mouth  with  antiseptics  during  an  epidemic  may 
reasonably  lu'  prartii-od.  luii  wiili  wliai  success  is 
uncertain.  The  aged  and  those  of  low  vitality 
should  avoid  exposure  to  infection^,  for  in  them  the 
severer  complications^  such  as  pneumonia,  are 
more  likely  to  occur.  When  influenza  conjuncti- 
vitis appears  epidemically  in  schools,  the  latter 
should  be  closed  or  the  infected  children  excluded. 
Immunity,  Sus-       Although  little  or  nothing  is  known  concerning 

ceptibilitv  and  »  .         t    ■  4.      • 

Recurrences,  the  possibility  of  a  natural  immunity  m  man,  ex- 
perience teaches  that  he  is,  on  the  whole,  very  sus- 
ceptible. The  belief  expressed  b}^  some  that  nurs- 
ing children  are  less  susceptible  tlian  older  people 
seems  to  have  some  foundation,  although  it  is  well 
Ivnown  that  they  are  not  entirely  immune.  Influ- 
enza is  sometimes  cited  as  an  infection  in  which 
one  attack  creates  a  predisposition  for  a  second, 
but  the  truth  of  this  is  doubted  by  many  who  have 
had  extensive  experience  with  the  disease.  Wutz- 
dorff,  in  a  study  of  the  epidemic  which  prevailed 
in  Germany  during  1891-92,  finds  in  the  small 
number  of  cases,  the  irregularity  of  their  distribu- 
tion, and  comparative  exemption  of  rather  large 
districts,  reasons  for  believing  that  one  attack  con- 
fers a  degree  of  acquired  immunity ;  that  is  to  say, 
the  population  had  been  so  thoroughly  infected 
(durchgeseucht)  during  the  preceding  year  or  two 
that  comparatively  few  remained  who  were  sus- 
ceptible, although  the  disease  itself  appeared  to  be 
more  malignant  than  in  the  previous  year  (cited 
from  Beck).     However,  the  occurrence  of  second 


CHANCROID. 


399 


Properties. 


attacks  shortly  after  the  first,  and  of  repeated  in- 
fections in  some  individuals  indicate  that  acquired 
immunity  is  of  short  duration.  The  aged,  those 
of  low  vitality,  and  those  with  pulmonary  tuber- 
culosis, have  low  resistance  to  infection. 

Although  Delius  and  Kolle  Avere  able  to  produce  seru 
a  slight  increase  in  the  resistance  of  guinea-pigs 
by  the  intraperitoneal  injection  of  cultures,  noth- 
ing like  a  well-marked  immunity  was  obtained; 
nor  did  the  serum  of  immune  animals  or  convales- 
cent man  show  increased  protective  power  for 
other  animals.  Slatineano,  however,  obtained 
serum  of  some  protective  value  for  guinea-pigs, 
by  the  immunization  of  rabbits  and  guinea-pigs, 
but  it  had  no  curative  effect.  The  results  of  Can- 
tani  were  similar,  and  both  observers  noted  the  de- 
velopment of  bactericidal  power,  as  determined  by 
the  Pfeiffer  reaction,  and  of  agglutinins.  At  the 
present  time  there  seems  little  to  hope  from  vac- 
cination. 

There  is  said  to  be  some  increase  in  agglutinins 
in  man  as  a  consequence  of  infection.  The  agglu- 
tinating power  of  the  serum  of  an  immunized  ani- 
mal may  be  as  high  as  1  to  500  (Cantani). 

VIII.    SOFT    CHANCRE. 

The  independence  of  soft  chancre  and  syphilis, 
and  the  infectiousness  of  the  former  by  inoculation 
with  the  purulent  secretions  of  the  ulcers,  were 
established  long  ago.     Rollet  found  that  filtered" 
pus  lost  its  infectiousness. 

A  large  number  of  observers  had  found  bacteria  Bacillus 
of  one  kind  or  another  in  the  pus  and  in  stained  o^oucrey. 
sections  of  the  walls  of  the  ulcers,  and  probably 
some  of  them  (e.  g.,  Unna),  had  seen  the  bacillus 


400  lyFECTIOX  AXD  IMMVXITY. 

wliich  Ducrcv  described  (188i))  and  later  culti- 
vated, ami  which  is  now  proved  to  be  the  cause  of 
tlie  disease.  The  bacillus  is  very  small  (0.4x1.5 
microns),  is  non-motile  and  shows  polar  staining. 
It  resembles  tlie  plague  bacillus  in  form,  but  is 
somewhat  smaller,  and  does  not  show  the  exten- 
sive involution  forms  of  the  latter.  In  the  ulcer 
it  lies  singly,  in  small  groups,  or  more  characteris- 
tically in  the  form  of  bands,  made  up  of  two  or 
more  parallel  chains,  which  infiltrate  the  wall  of 
the  ulcer.  Large  numbers  are  often  found  in  the 
pohTnorphonuclear  leucocytes  of  the  pus,  par- 
ticularly at  an  early  stage  of  the  lesion  (Kroeft- 
ing).  Great  difficulty  was  encountered  in  culti- 
vating the  bacillus,  and  Ducrey's  first  success  was 
obtained  with  a  medium  w^hich  contained  human 
skin.  It  has  since  been  cultivated  on  agar  which 
contains  the  blood  or  serum  of  man,  rabbit  or 
dog.  Himmel  attempted  to  cultivate  it  in  the 
fresh  defibrinated  blood  of  the  guinea-pig,  but 
was  unsuccessful  because  the  bacilli  were  phago- 
cytized  by  the  leucocytes  (Babes). 

An.  ulcer  resembling  that  of  soft  chancre  may 
be  produced  in  the  ape,  and  also  in  the  cat,  by  the 
inoculation  of  pure  cultures.  Didey  reinoculated 
man,  successfully,  from  the  ulcers  of  the  cat. 
When  living  cultures  are  injected  into  the  guinea- 
pig  (peritoneal  cavity,  subcutaneous  tissue,  dura 
mater),  the  bacilli  are  quickly  taken  up  by  leuco- 
cytes and  digested  (Himmel).  Himmel  reports 
having  so  decreased  the  resistance  of  guinea-pigs 
by  peritoneal  injections  of  lactic  acid  that  they 
became  susceptible  to  infection.  After  two  or 
three  passages  the  culture  became  so  virulent  that 


CAP8ULATED  BACILLI.  401 

fatal  bacteriemia  was  caused  without  previously 
lowering  the  resistance  of  the  animals. 

In  man  the  infection  is  transmitted  to  the  in- 
guinal lymph  glands,  but  never  becomes  general. 

One  attack  in  man  does  not  confer  lasting  im- 
munity. SiDontaneous  recovery  occurs,  but  its 
cause  is  not  known.  Inasmuch  as  the  bacilli  are 
found  within  leucocytes,  phagocytosis  may  be  a 
factor  in  recovery.  The  readiness  with  which  the 
autoinoculation  of  adjacent  skin  takes  place,  even 
after  the  disease  has  existed  for  some  time,  sug- 
gests that  general  immunity  is  not  established. 

IX.    BACILLUS    OF    FKIEDLANDER    AND    OTPIER    MEM- 
BEES    OF    THE    CAPSULE-FORMING    GROUP. 

The  bacillus  of  Friedlander,  or  Bacillus  pneu-  capsuiated 
moniwj,  is  the  type  of  a  rather  large  group  of  bac-  ^^"^'"'• 
teria,  called  the  Friedlander  group,  or  the  group 
of  Bacillus  mucosus  capsulatus.  In  addition  to 
the  ability  to  produce  a  mucus-like  capsule  or  en- 
velop, they  have  in  general  the  following  charac- 
teristics (Abel)  :  short,  plump  rods,  varying  in 
their  proportions,  having  no  motion,  no  flagella, 
no  spore  formation,  and  not  staining  by  Gram's 
method.  They  form  mucus-like  masses  in  cul- 
tures, do  not  liquefy  gelatin  and  are  facultative 
anaerobes.  They  are  widely  distributed  in  nature, 
vary  from  innocuousness  to  extreme  pathogenicity 
for  animals,  are  rarely  found  in  the  mouth,  nose 
and  bronchi  normally  (bacillus  of  Friedlander), 
one  type  being  a  normal  inhabitant  of  the  intes- 
tines, especially  in  children  (B.  laciis  aerogenes). 
Perkins  has  been  able  to  classify  the  members  of 
this  group  on  the  basis  of  their  fermenting  powers 
for  lactose  and  saccharose.     He  found  their  viru- 


402 


INFECTION  AND  IMMUNITY. 


Pneumonia 

Caused  by 

Friedlander's 

Bacillus. 


Rhinoscleroma 
and  Ozena. 


lence  for  anilnal!^,  iniiiuinizatidii  and  agglutination 
tests,  too  variable  to  serve  as  bases  for  classifica- 
tion. In  man  three  members  of  the  group — they 
may  be  the  same  organism  or  variations  of  a  type 
— are  of  interest  from  the  standpoint  of  infection : 
Bacillus  of  Friedlander,  the  bacillus  of  rhinoscle- 
roma and  the  ozena  baeilhis. 

In  129  cases  of  acute  inflammation  of  the  lungs, 
Weichselbaum  found  the  bacillus  of  pneumonia 
nine  times,  twice  with  streptococci  and  once  with 
the  diplococcus  of  pneumonia.  The  organism 
causes  lobular  pneumonia  more  frequently  than 
lobar.  The  homogeneous  non-granular  surface, 
and  the  large  amount  of  fluid  of  a  viscid  or  mu- 
cous consistence,  are  characteristic  anatomic  feat- 
ures. The  alveoli  contain  massive  numbers  of  the 
bacilli.  The  bacillus  of  Friedlander  is  found  also 
as  the  cause  of  pyelitis,  cystitis,  pyelonephritis, 
serous  or  purulent  pericarditis,  pleuritis  and 
meningitis,  which  may  be  accompanied  by  brain 
abscesses.  Meningitis  when  produced  by  this  or- 
ganism usually  or  always  is  secondary  to  infection 
in  other  parts  of  the  hody  by  the  same  organism 
(middle  ear  and  accessory  sinuses  of  the  nose). 

An  organism  of  the  Friedlander  type  is  found 
with  few  exceptions  in  the  tissues  in  rhinoscle- 
roma, and  by  many  is  considered  as  the  cause  of 
the  condition.  A  similar  organism  is  found  con- 
stantly in  the  secretions  and  crusts  in  ozena. 

Antiserums  of  distinct  power  have  not  been  ob- 
tained for  members  of  the  group.  Prolonged  im- 
munization with  pome  strains  yields  an  agglutinat- 
ing serum  of  low  value.  The  agglutination  re- 
action  is  of  no  value  for  identification  of  the  dif- 
ferent members  of  the  group,  nor  for  clinical 
diagnosis. 


RELAPSING   FEVER. 


403 


X.     RELAPSING   FEVER.    ■ 

In  1868  Obermeier  discovered  in  the  blood  of  The  Parasite. 

patients  suffering  from  relapsing  fever,  "very  fine 
threads  exhibiting  motility'^ ;  these  "threads"  have 
since  been  known  as  the  Spiroclieta  ohermeieri.* 
and  are  recognized  as  the  cause  of  the  disease. 
They  are  very  thin  (about  1  micron),  from  10  to 
40  microns  in  length,  and  of  spiral  form.  Three 
types  of  motion  are  described :  a  screw-like,  a  for- 
ward and  backward  movement  and  a  lateral  bend- 
ing. They  are  found  only  in  the  blood  and  blood- 
forming  organs.  They  disappear  from  the  blood 
with  remarkable  rapidity  at  the  time  of  crisis,  al- 
though they  may  be  found  in  the  spleen  one  or 
two  days  later. 

The  organism  has  not  been  grown  artificially, 
but  it  may  be  kept  alive  for  a  number  of  days  in 
the  blood  or  serum  of  patients.  As  the  micro-or- 
ganisms die  agglomerations  are  formed  and  they 
undergo  granular  changes. 

The   organism   is   not  found   in   Nature,   and.  Transmission 
since  it  occurs  only  in  the  blood  of  the  sick,  it  has 
long  been  assumed  that  infection  can  be  accom- 
plished only  by  the  inoculation  of  infected  blood. 


*  This  organism  is  sometimes  called  a  spirillum,  incor- 
rectly. The  spirillaceoe,  Migula's  third  family  under  the 
Order  of  Eubacteria,  comprises  organisms  with  these  char- 
acteristics :  "Cells  which  are  twisted  screw-fashion  or  repre- 
sent a  segment  of  a  spiral.  Division  takes  place  only  in  one 
direction  of  space  after  the  cell  has  elongated."  The  dif- 
ference between  spirillum  and  spirochseta  is  shown  by  the 
following :  "3.  Genus :  Spirillum.  Cells  rigid,  with  polar 
tufts,  for  the  most  part  bent  in  the  form  of  a  half-circle, 
as  organs  of  locomotion.  4.  Genus :  Spirochseta.  Cells  with 
snake-like  bending,  organs  of  locomotion  unknown." 
Although  Migula  classes  this  organism  with  the  bacteria, 
there  is  some  ground  for  considering  it  protozoon  in  nature. 


404  IXl'ECTIOy  SyO  IMMUNITY. 

The  parasites  have  been  demonstrated  repeatedly 
in  bedbugs  wliieh  are  found  on  the  mattresses  of 
the  sickbed,  and  monkeys  liave  been  infected  by 
inocuhiting  them  with  the  blood  found  in  the 
bodies  of  these  insects,  and  by  the  bites  of  the  lat- 
ter (Tictin).  It  is  said  that  they  may  remain 
alive  in  bedbugs  for  as  long  as  thirty  days.  It  is 
not  altogether  excluded  that  other  vermin  also 
transmit  the  disease. 

The  spirocheta  does  not  appear  in  any  of  the  ex- 
cretions, unless  they  happen  to  be  of  a  bloody 
character. 

Certain  monkeys,  those  belonging  to  the  slender- 
nosed  family  (Catarrliince),  may  be  infected  by 
injecting  the  blood  of  patients,  provided  the  blood 
used  is  taken  during  the  paroxysm,  i.  e.,  at  a  time 
when  the  microbes  are  Imown  to  be  in  the  blood. 
]\Ionkeys  do  not  contract  the  disease  under  natural 
conditions.  Other  .  animals  are  not  susceptible. 
The  incubation  period  in  man  usually  is  from  five 
to  seven  days,  and  in  monkeys  from  one  and  one- 
half  to  four  days.  Cloudy  swelling  of  the  paren- 
chymatous organs,  ecchymoses  and  infarcts  of  the 
sjileen  and  kidneys  are  found  in  fatal  cases. 

Prophylaxis  consists  in  isolation  of  the  patient, 
cleanliness,  and  the  destruction  of  vermin,  espe- 
cially bedbugs. 

Eelapsing  fever  occurs  in  various  races  of  man, 
and  so  far  as  Imown  none  are  immune.  Osier  states 
that  in  the  United  States  the  disease  has  not  been 
seen  since  1869,  when  it  was  epidemic  in  ISTew 
York  and  Philadelphia.  The  natural  immunity  of 
other  animals  is  referred  either  to  phagocytosis 
or  to  normal  bacteriolysins,  but  the  conditions 
probably  are  not  thoroughly  understood. 


RELAPSING   FEVEIt. 


405 


As  stated  above,  a  remarkable  feature  in  the  Phaciotytosis 
course  of  the  disease  is  the  rapidity  with  which  the  lysins. 
micro-organisms  disappear  from  the  blood  at  the 
time  of  the  crisis.  MetchnikofE  refers  this  to 
phagocytosis  by  the  microphages,  which  undergo 
a  progressive  increase  during  the  paroxysm  and 
decrease  after  the  crisis.  Very  little  phagocytosis 
appears  to  take  place  in  the  circulating  blood,  but 
in  the  spleen  many  spirochetse  are  found  within 
polymorphoneuclear  leucocytes.  Tictin  also  found 
them  in  the  parenchymatous  cells  of  the  kidney, 
liver  and  lungs.  Phagocytosis  is  most  marked  at  or 
near  the  time  of  the  crisis.  According  to  Metchni- 
koff,  relapse  or  reinfection  is  accomplished  ^by 
spirochet^e  Avhich  again  invade  the  body  from  the 
spleen. 

Eussian  observers  have  studied  the  development 
of  a  specific  bactericidal  power  in  the  serum  of  the 
sick  and  in  animals  which  were  immunized  by  the 
injection  of  infected  blood  from  man.  Inasmuch 
as  the  organism  can  not  be  cultivated,  bactericidal 
tests  must  be  performed  with  the  organisms  as 
they  occur  in  the  blood  or  serum  of  the  patients, 
and  Gabritschewsky  has  devised  a  technic  for  this 
procedure. 

A  drop  of  serum  from  an  immune  animal  or  a  Technic. 
convalescent  patient  is  mixed  on  a  slide  with  a 
drop  of  serum  which  contains  the  spirocheta,  the 
latter  serum  being  taken  from  a  patient  during  an 
attack.  The  preparation  is  sealed  under  a  cover- 
glass  and  examined  at  intervals,  and  the  death  of 
the  organisms  is  determined  by  their  loss  of  mo- 
tility. It  is  said  that  the  bactericidal  power  of 
human  blood  following  infection,  and  that  of  im- 
munized animals,  is  increased. 


40G  IM'KCTWX  A'SD  IMMUNITY. 

Active  In  view  of  the  facts  that  three  or  more  relapses 
sive  Immunity,  may  occur  and  that  reinfection  is  possible  at  a 
later  period,  it  seems  probable  that  man  does  not 
readily  acquire  immunity  to  the  infection,  al- 
though second  and  third  relapses  are  said  to  be 
lighter  than  the  first.  Monkeys  which  have  been 
artilicially  infected  several  times  acquire  some 
resistance  to  the  disease.  The  view  of  Metch- 
nikoff  that  the  spleen  is  essentially  involved  in 
recovery  and  immunity  seems  to  have  been  dis- 
proved l)y  the  experiments  of  Tictin,  who  found 
that  splenectomy  had  no  influence  on  recovery  or 
the  development  of  immunity. 

The  serum  of  convalescents  affords  a  certain  de- 
gree of  protection  to  the  monkey  ( Gabritschew- 
sky) .  Loventhal  utilized  the  serum  of  immunized 
horses  in  the  treatment  of  the  disease  in  man,  and 
reported  a  decrease  in  the  number  and  severity  of 
relapses.  The  action  of  the  serum  has  been  re- 
ferred both  to  its  content  in  bactericidal  antibodies, 
and  to  its  ability  to  stimulate  phagocytosis. 

Melkich  states  that  agglutinins  are  formed  and 
that  they  appear  on  from  tlie  third  to  the  fifth 
day  of  the  disease. 


A  rapidly  fatal  disease  of  geese,  spirocheta  septi- 
cemia, or  spirillosis  of  geese,  is  caused  by  an  or- 
ganism which  resembles  the  spirocheta  of  OIkt- 
meier,  and  a  similar  infection  has  been  noted  in 
chickens  in  Brazil  and  in  cattle  in  the  Transvaal. 


GEOUP  IV. 


Infectious  diseases  which  usually  are  chronic, 
but  may  run  acute  courses.  They  are  characterized 
by  marked  local  tissue  changes,  which  exert  a  lim- 
iting influence  on  the  processes,  and  include  the 
infectious  granulomata,  excepting  syphilis.  Infec- 
tion produces  little  or  no  immunity.  In  some  in- 
stances the  prolonged  immunization  of  animals  in- 
duces increased  resistance  to  infection  (tuberculo- 
sis) ;  in  other  instances  this  has  not  been  deter- 
mined, or  is  difficult  of  determination  because  of 
the  non-susceptibility  of  experiment  animals  to 
the  corresponding  infections.  The  serums  of  im- 
munized animals,  in  so  far  as  this  subject  has  been 
investigated,  show  little  or  no  protective  or  cura- 
tive power. 

I.    TUBEKCULOSIS. 

Klemke,  in  1843,  but  more  particularly  Ville- 
min,  in  1865,  demonstrated  the  infectiousness  of 
tuberculosis  by  animal  experiments,  and  these  re- 
sults were  substantiated  later  by  such  investigators 
as  Klebs,  Chauveau,  Baumgarten  and  Conheim. 
Baumgarten  first  saw  the  tubercle  bacillus  in  sec- 
tions of  tuberculous  material  from  which  the  tis- 
sue cells  had  been  dissolved  by  potassium  hydroxid, 
and  at  almost  the  same,  time  Koch  succeeded  in 
demonstrating  its  presence  in  all  tuberculous 
lesions  by  a  special  staining  method.  He  eventu- 
ally obtained  the  organism  in  pure  cultures  with 
which  he  again  produced  tiiberculosis  in  experi- 
ment animals. 

The  tubercle  bacillus  is  an  obligate  aerobic  para- 
site, has  the  form  of  a  slender,  non-flagellated  rod. 


408 


IXFECTIOy    AMJ    IMMUMTY. 


Characteristics 
of  the  Bacillus. 


Staining 
Properties. 


often  sliglitly  curved,  from  2  to  4  microns  long 
and  from  0.3  to  0.5  microns  broad.  In  stained  and 
even  in  unstained  specimens,  when  properly 
treated,  a  number  of  spherical,  oval  or  elongated 
clear  spaces  can  be  seen  which  Koch  at  one  time 
thought  to  be  spores.  They  are  now  considered 
cither  as  vacuoles,  or  as  representing  some  form  of 
degeneration  or  reserve  nutritious  material.  Spore 
formation  is  uncertain.  The  organism  is  sup- 
posed to  possess  a  membrane  which  may  be  re- 
sponsible for  its  strong  resistance  against  heat  and 
desiccation.  Feinberg  speaks  of  a  nucleus  (  ?)  which 
may  be  demonstrated  by  a  modified  Romanowsky 
stain.  The  organism  shows  many  variations  in  its 
morphology  under  different  conditions.  It  often 
exists  in  isolated  clumps,  either  in  cultures  or  in 
tissues,  and  may  be  excreted  as  such  in  the  urine. 
In  certain  cultures  and  sometimes  in  animal  tis- 
sues it  grows  in  the  form  of  longer  or  shorter 
branching  threads,  in  this  respect  resembling  acti- 
nomyces.  This  last  occurrence  has  led  a  number 
of  authorities  to  class  the  tubercle  bacillus  as  a 
streptothrix,  while  others  would  give  it  an  inter- 
mediate position  between  true  l)acteria  (schizomy- 
cetes)  and  the  streptothrix  (a  hyphomyces).  Oval 
or  spherical  degeneration  forms,  the  capsules  or 
corpuscles  of  Schron,  are  found  in  advanced  tuber- 
culosis of  the  lymph  glands  and  other  organs  in 
which  there  is  a  great  deal  of  necrosi?. 

The  tubercle  bacillus  is  one  of  a  group  of  organ- 
isms Avhich  are  said  to  be  "acid  fast"  in  their 
staining  properties.  When  stained  with  the  carbol 
fuchsin  of  Ziehl  and  subjected  to  the  action  of 
mineral  acids  in  dilute  solutions  the  fuchsin  is  not 
removed..    After  counterstaining  with  methylene 


TUBEJWULOHfS. 


409 


blue,  the  tubercle  bacilli  appear  red,  whereas  other 
organisms,  not  "acid  fast,"  are  stained  with  the 
methylene  blue.  It  is  not  diflicult  to  recognize  the 
bacilli  in  sections  of  tissue  when  the  proper  technic 
is  used,  although  the  search  is  at  times  a  laborious 
one.  In  old  processes  the  organism  often  can  not 
be  recognized,  and  recourse  to  animal  inoculation 
may  be  necessary  in  order  to  demonstrate  the  ex- 
istence of  tuberculosis. 

It  is  ordinarily  a  difficult  task  to  obtain  the  Cultivation. 
tubercle  bacillus  in  pure  culture,  the  technic  of 
which  we  need  not  consider.  Even  under  the  best 
conditions  growth  is  very  slow,  and  may  not  be 
recognizable  to  the  naked  eye  for  from  six  to  ten 
days.  Coagulated  serum  of  the  cow  to  which  has 
been  added  from  2  to  4  per  cent,  glycerin  is  the 
most  favorable  culture  medium.  Good  growth  oc- 
curs also  in  glycerin  agar,  in  glycerin  bouillon 
and  on  potatoes.  The  optimum  temperature  is  37° 
C;  growth  does  not  occur  above  42°  C.  nor  below 
30°  C.  When  a  small  amount  of  culture  is  planted 
on  the  surface  of  glycerin  bouillon  it  proliferates 
slowly  to  form  a  heavy  membrane.  In  time  this 
growth  sinks  from  its  own  weight  and  a  new  mem- 
brane forms.  This  process  continues  until  large 
masses  have  accumulated  at  the  bottom  of  the 
flask. 

In  its  resistance  to  desiccation  the  tubercle  ba-  Resistance. 
cillus  is  exceeded  only  by  spore-forming  organisms ; 
it  lives  approximately  for  three  months  in  dried 
sputum  which  appears  to  form  a  protective  coat- 
ing about  it.  Direct  sunlight  destroys  it  in  a  few 
hours  at  the  most,  whereas  diffuse  light  kills  it 
only  after  from  five  to  seven  days  (Koch).  It  is 
said  that  the  guinea-pig  when  exposed  to  sunlight 


410  lyFKCTIOX    AXD    IMMUXITY. 

■  witlistaiuls  luborculosis  for  a  longer  time  than  one 
which  is  kept  in  tlie  dark.  Eoeutgen  rays  are  bac- 
tericidal for  tlie  organism,  killing  it  in  about  one 
hour  (Rieder).  Under  moist  heat  a  temperature 
of  55°  C.  kills  it  in  from  four  to  six  hours,  60°  C. 
in  one  hour,  70°  C.  in  from  ten  to  twenty  minutes, 
80°  C.  in  five  minutes,  from  90°  to  95°  C.  in  from 
one  to  two  minutes.  When  embedded  in  sputum 
it  is  more  resistant,  five  minutes  being  required  to 
kill  it  at  the  boiling  temperature.  Corrosive  sub- 
limate is  not  a  good  disinfectant  in  this  case,  inas- 
much as  it  produces  an  albuminous  precipitate 
around  the  organism  which  prevents  penetration 
of  the  sublimate.  Five  per  cent,  carbolic  acid 
added  to  equal  parts  of  sputum  kills  the  bacillus  in 
twenty-four  hours.  Formalin  vapor  is  a  good  dis- 
infectant for  dr}',  but  not  for  moist  sputum.  Iodo- 
form is  not  a  good  disinfectant,  in  spite  of  its  bene- 
ficial influence  on  the  infectious  process.  The  re- 
sistance of  the  bacillus  to  gastric  digestion  lias  an 
important  bearing  on  the  occurrence  of  infection 
in  the  intestinal  tract.  The  gastric  juice  of  the 
dog,  in  one  instance,  failed  to  kill  the  bacillus  after 
six  hours'  exposure,  although  it  had  the  power  of 
prohibiting  proliferation. 
Virulence.  The  bacillus  of  liuman  tuberculosis,  although 
fairl}'  constant  in  its  virulence,  may  be  attenuated 
by  various  means.  Its  prolonged  existence  in  putrid 
sputum  decreases  its  virulence  and  a  similar  de- 
crease occurs  on  potato,  in  old  cultures  or  in  those 
w^hicli  contain  iodoform,  boracic  acid  and  some 
other  substances.  Inoculation  with  such  cultures 
produces  a  chronic  form  of  tuberculosis  in  animals 
which  may  heal.  In  other  instances  cultures  which 
have  grown  on  artificial  media  for  many  years  re- 
tained their  original  virulence. 


TUBERCULOmB.  411 

The  organism  contains  about  90  per  cent,  of 
water.  One-fourth  of  a  dried  bacterial  mass  may 
be  extracted  as  a  wax-like  or  fat-like  substance  by 
a  mixture  of  alcohol  and  ether.  The  acid-fast 
staining  property  of  the  bacillus  depends  on  this 
substance.  The  remaining  portion  of  the  mass, 
consisting  largely  of  proteins,  which  may  be  ex- 
trated  by  dilute  alkalies,  contains  a  toxic  nucleo- 
albumin.  Cellulose,  representing  a  portion  of  the 
capsular  substance,  is  also  found  in  the  residue. 

Killed  cultures  when  given  subcutaneouslv  pro-  Toxic 

,  .  ,  °  . .  1     Products. 

duce  necrosis,  abscesses,  caseation,  marasmus,  ana 
a  subnormal  temperature.  Wlien  given  to  rabbits 
and  guinea-j^igs  intravenously  they  cause  rapid 
emaciation  and  death  in  from  a  few  days  to  a  few 
weeks.  By  beginning  with  very  minute  doses,  how- 
ever, the  animals  may  be  gradually  habituated  to 
intoxication  by  the  dead  bacilli  and  eventually 
withstand  large  doses.  The  same  holds  true  of  the 
various  toxic  substances,  including  tuberculin, 
which  may  be  extracted  from  cultures.  The  pro- 
teins and  alkaline  extracts  cause  abscesses  when 
given  subcutaneously.  The  fever -producing  sub- 
stance which  is  present  in  the  preparations  men- 
tioned below  is  one  of  the  metabolic  products  of 
the  bacillus,  rather  than  a  constituent  of  the  bac- 
terial cell  (Koch).  This  substance  is  100  times 
as  toxic  for  tuberculous  animals  as  for  healthy  and 
causes  an  increase  in  the  eosinophiles  of  the  blood.  • 
In  addition  to  the  fever-producing  substance, 
Maragliano  and  others  recognize  as  a  constituent 
of  the  bacillus  a  heat  susceptible  "toxalbumin'^ 
(destroyed  at  100°  C.)  which  reduces  temperature. 
Hammerschlag  speaks  of  a  toxin  which  in  animals 
causes  fatal  convulsions.  The  toxic  products  of  the 


412  IXrECTIOX    A\D    TMMTXITY. 

-  tubercle  bacillus  show  their  greatest  toxicity  when 
injected  into  tlie  brain,  and  this  method  of  injec- 
tion has  been  suggested  for  the  standardization  of 
tuberculin. 

lubercuiin.  Of  the  toxic  preparations  of  the  bacillus  the 
greatest  interest  attaches  to  tuberculin  which 
Koch,  in  1891,  announced  as  an  agent  which  could 
be  used  for  the  specific  diagnosis  of  tuberculosis 
and  which,  when  properly  administered,  had  cer- 
tain curative  effects.  Its  ^preparation  is  simple. 
Cultures  are  allowed  to  grow  for  four  weeks  in 
peptone  bouillon  which  coiitains  5  per  cent,  of 
glycerin.  At  the  end  of  this  time  the  organisms 
are  killed  by  exposure  to  a  temperature  of  100°  C. 
for  one  hour  (Marx).  The  fluid  is  reduced  to  one- 
tenth  its  original  volume  by  evaporation  under  a 
vacuum  at  a  low  temperature  and  the  bacterial 
cells  are  eventually  removed  by  filtration.  The 
percentage  of  glycerin  which  is  present  in  the  final 
preparation  acts  as  a  preservative,  but  0.5  per 
cent,  carbolic  acid  may  be  added  in  addition.  The 
active  substance  in  tuberculin  may  be  precipitated 
by  66  per  cent,  alcohol;  its  chemical  nature  re- 
mains imlvuown.. 

"ta,"^^"tr;|  In  addition  to  the  "old  tuberculin,"'  which  has 
just  been  described,  Koch  has  made  several  other 
preparations  having  similar  properties,  the  use  of 
■which  has  been  proposed  for  diagnostic  and  cura- 
*tive  purposes  and  for  convenience  in  carrying  out 
the  agglutination  reaction.  One  of  these,  "TA," 
is  an  alkaline  preparation  which  is  made  by  ex- 
tracting cultures  with  1/10  normal  sodium  hy- 
droxid  solution.  Its  value  as  a  diagnostic  was 
equal  to  or  exceeded  that  of  tuberculin  because  of 
the  longer  duration  of  the  reaction.     In  view  of 


TUBERCULOHIH.  413 

the  fact,  however,  that  it  contained  undissolved 
cells,  whicli  caused  the  formation  of  abscesses  at 
the  point  of  injection,  its  use  was  not  encouraged. 
For  purposes  of  immunization  Koch  prepared  a 
fluid  which  contained  all  the  bacterial  constituents 
and  which  at  the  same  time  is  readily  absorbed 
without  abscess  formation.  For  its  preparation 
dried  masses  of  the  organism  are  ground  up  in  an 
agate  mortar;  after  suspension  in  distilled  water 
and  centrifugation,  the  emulsion  consists  of  two 
layers.  The  overlying  opalescent  whitish  fluid  was 
designated  as  "TO"  {Tuberculin-Ohers).  After 
removal  of  the  fluid  from  the  precipitate  the  lat- 
ter was  again  dried  and  ground,  suspended  in 
water  and  centrifugated  as  before,  and  the  process 
.repeated  until  none  of  the  sediment  remained.  The 
different  fractions  of  fluid,  except  the  "TO,"  were 
combined  to  constitute  "TE"  {Tuberculin-Rest) , 
which  is  really  an  emiilsion  of  minute  fragments 
of  cells.  It  is  readily  absorbed  and  does  not  cause 
the  formation  of  abscesses.  This  is  commonly 
called  Koch's  "new  tuberculin."  Still  another 
preparation  which  Koch  has  recently  devised  for 
active  immunization  and  for  convenience  in  per- 
forming the  agglutination  test  consists  of  dried 
and  ground  iip  bacilli  which  are  suspended  in 
equal  parts  of  glycerin  and  water,  NeutuhercuUn 
Koch  (Bazillenemusion) . 

Preparations  which  in  many  respects  are  analo-  other 
gous  to  those  of  Koch  have  been  made  by  different 
investigators;  the  tuberculocidin  of  Klebs,  the  tu- 
berculins of  de  Schweinitz  and  Porset  and  that  of 
Denys,  the  two  toxins  of  tuberculins  of  Maragliano, 
which  he  utilizes  for  the  preparation  of  antitoxic 
serums,   the   oxytuberculin   of   Herschfelder,   the 


414 


INI'IJCTIOX    AM>    IMMl'MTY. 


Standard- 
ization. 


Dissemination. 


'"TD"  aud  the  "TDR"  of  Behring-  and  the  tubercu- 
loplasmin  of  Buchner.  Marmorek  claims  to  have 
obtained  the  true  toxin  of  the  tubercle  bacillus  by 
iiTowing  young,  vigorous  cultures  on  a  complicated 
medium,  denying  that  tuberculin  represents  the 
true  toxin  of  the  organism. 

Tuberculin  can  not  be  standardised  with  accur- 
acy. Because  of  the  extraordinary  susceptibility  of 
tuberculous  animals  to  tuberculin,  Koch  decided  to 
estimate  its  value  by  the  quantity  required  to  kill 
such  animals.  From  0.5  to  1  c.c.  of  tuberculin, 
when  injected  into  a  healthy  guinea-pig,  causes 
neither  a  local  nor  a  general  reaction,  whereas 
from  0.1  to  0.15  c.c.  kills  a  tuberculous  guinea- 
pig  in  from  twentj'-four  to  forty-eight  hours.  For 
standardization  von  Lingelsheim  recommends  in- 
tracerebral injection  into  healthy  guinea-pigs,  be- 
cause of  the  extreme  toxicity  of  tuberculin  when 
introduced  into  the  central  nervous  system;  only 
1/180  as  much  tuberculin  was  required  to  cause 
death  by  intracerebral  injections  as  compared  with 
subcutaneous  or  intraperitoneal.  Behring  bases  the 
value  of  tuberculin  on  its  toxicity  for  healthy 
guinea-pigs  and  in  his  terms  the  expression  "1 
c.cm.  =  1,000  M."  means  that  one  gram  of  the 
toxin  is  fatal  to  1,000  grams  of  guinea-pig  tissue. 
His  "TD"  has  a  value  of  1,250  M.,  and  ''TDR," 
12,500  M. 

The  tubercle  bacillus  undergoes  no  proliferation 
outside  the  body  and  its  occurrence  in  nature  de- 
pends on  the  distribution  of  the  infected  excre- 
tions, particularly  the  sputum,  of  man.  Hence  it 
is  found  most  abundantly  in  the  rooms  and  homes 
of  patients  and  in  tuberculous  wards  of  hospitals. 
Reception  of  sputum  on  the  handkerchief  of  the 


TUBERCTJLOHIH. 


415 


patient,  where  it  subsequently  dries,  and  its  dis- 
charge on  the  floor  in  public  places,  where  it  quick- 
ly becomes  pulverized,  as  in  street  cars,  are  condi- 
tions which  favor  dissemination  and  the  infection 
of  others.  In  unconfined.  places  which  are  exposed 
to  the  action  of  light  and  sun,  as  the  streets  and 
sidewalks,  the  danger  is  less  on  account  of  the 
shorter  life  of  the  organism  under  these  conditions 
and  the  greater  volume  of  surrounding  air.  The 
calculation  of  Heller  that  a  tuberculous  patient 
may  excrete  7,200,000,000  of  bacilli  in  a  day  sug- 
gests the  number  which  may  lurk  in  a  single  mis- 
placed portion  of  sputum.  Sputum  which  is  Jcept 
moist  is  not  a  source  of  particular  danger,  inas- 
much as  ordinary  currents  of  air  do  not  dissipate 
it  in  the  form  of  infected  drops.  Droplets  of  spu- 
tum which  are  expelled  by  coughing  contribute 
greatly  to  the  infected  dust  which  surrounds  a  pr  ■ 
tient. 

Large  quantities  of  bacilli  are  often  excreted  i:i 
the  feces  in  intestinal  tuberculosis  and  in  the  urine 
in  genitourinary  tuberculosis,  or  in  general  miliary 
tuberculosis  with  localization  of  the  process  in  the 
urinary  organs.  The  pus  from  tuberculous  ab- 
scesses commonly  is  infectious. 

Great  interest  attaches  to  the  possibility  of  infec- 
tion of  man  by  the  milk  and  meat  of  tuberculous 
cattle.  Previous  to  1901,  through  the  work  of 
Smith  and  others,  the  opinion  had  been  gaining 
ground  that  the  bacilli  of  human  and  bovine  tuber- 
culosis are  not  identical.  It  was  not  always  possi- 
ble to  produce  tuberculosis  in  cattle  by  feeding 
them  or  causing  them  to  inhale  tuberculous  spu- 
tum or  pure  cultures  which  were  highly  infectious 
for  other  experiment  animals,  although  bacilli  of 


Dried 
Sputum 


Bovine 
and  Human 
Tuberculosis. 


41G  INFECTION    AND    IMMUNITY. 

bovine  origin  invariably  cansod  the  disease  in  cattle 
when  administered  in  a  similar  manner.  It  seemed 
then  that  the  two  bacilli  are  not  identical  in  their 
pathogenic  powers.  Koch  having  performed  such 
experiments  without  being  able  to  infect  cattle  with 
bacilli  of  human  origin  expressed  his  belief  that 
the  converse  also  is  true,  i.  e.,that  the  bovine  ba- 
cillus is  not  pathogenic  for  man.  Perhaps  the 
strongest  argumeiit  in  favor  of  this  view  is  the 
circumstance  that  primary  tuberculosis  of  the  ines- 
tines  and  mesenteric  glands  is  very  rare  in  chil- 
dren, who  drink  a  good  deal  of  milk,  in  spite  of 
the  great  prevalence  of  tuberculous  cows.  ]\[any 
protests  folloAved  the  announcement  of  Koch's 
views,  and  in  a  short  time  a  number  of  investiga- 
tors showed,  first',  that  it  is  possible  in  some  cases 
to  produce  tuberculosis  in  cattle  with  tuberculous 
material  from  man,  and,  second,  that  infection  of 
man  with  tlie  bovine  bacillus  is  possible.  Un- 
questionable proof  of  the  latter  consists  in  the  de- 
velopment of  localized  tuberculosis  in  those  who 
have  performed  autopsies  on  tuberculous  cattle 
(Kavanel  and  others).  These  occurrences,  of 
course,  do  not  prove  the  identity  of  the  two  organ- 
isms, for  there  is  still  abundant  reason  to  believe 
that  the  two  bacilli  are  most  pathogenic  for  their 
respective,  natural  hosts,  and  much  less  pathogenic 
for  the  alternative  hosts.  Theobald  Smith  has 
pointed  out  that  many  experiments  in  which  the 
pathogenicity  of  the  human  bacillus  for  cattle  was 
investigated  by  the  feeding  of  tuberculous  sputum 
must  be  repeated,  inasmuch  as  it  was  not  deter- 
mined in  advance  whether  the  organism  contained 
in  the  sputum  was  of  the  human  or  bovine  type. 
Xaturally,  absolute  conclusions  as  to  the  patho- 


TUBERCULOSIS.  417 

genicity  of  the  human  bacillus  for  cattle  could  not 
be  drawn  with  this  fact  undetermined.  In  some 
cases  the  combined  sputum  from  many  patients 
has, been  fed  to  cattle,  and,  since  both  human  and 
bovine  bacilli  may  have  been  administered,  the  re- 
sults are  valueless  in  relation  to  the  point  under 
discussion.  In  each  instance  the  organism  should 
be  obtained  in  pure  culture,  its  identity  as  a  human 
or  bovine  bacillus  determined  and  the  experiment 
performed  with  such  pure  cultures.  The  following 
points  serve  to  distinguish  the  bovine  bacillus  from 
the  human:  First,  the  bovine  bacillus  is  shorter  Differences  in 
than  the  human;  second,  when  first  cultivated  it 
grows  feebly  in  media  in  which  the  human  bacil- 
lus flourishes;  third,  it  has  a  higher  virulence  for 
rabbits  and  guinea-pigs,  and,  fourth,  it  produces 
more  extensive  lesions  in  cattle.  To  these  Smith 
has  added  a  fifth  point,  which  he  has  found  to  be 
distinctive  in  a  large  number  of  cultures.  In 
bouillon  which  contains  5  per  cent,  of  glycerin  and 
which  is  2  per  cent,  acid  to  phenol  phthalein  the 
bovine  bacillus  produces  a  neutral  or  faintly  alka- 
line reaction  in  from  three  to  several  weeks,, 
whereas  the  human  bacilhis,  after  causing  tempo- 
rary alkalinity,  produces  a  terminal  acidity  of 
from  0.5  to  1.5  per  cent.  On  the  basis  of  this  test 
and  other  points  the  bacilli  of  two  cases  of  mesen- 
teric tuberculosis  in  man  were  recognized  as  bo- 
vine in  type.  In  view  of  the  fact  that  infection  of 
man  with  the  bovine  bacillus  has  been  shown  to  be 
possible,  we  are  still  justified  in  considering  the 
meat  and  especially  the  milk  of  tuberculous  cattle 
as  the  probable  sources  of  infection  in  a  limited 
number  of  cases. 

Comparatively  few  cases  of  undoubted  congeni- 


418  INFECTION    AND    I}rMUNITT. 

Congenital  ttil  tuborculosis  liavc  becii  observed,  and  in  such 

Tuberculosis.  n       • 

cases  the  mothers  are  usually  in  an  advanced  stage 
of  the  disease.  It  is  probable  that  the  organisms 
reach  the  fetus  following  metastatic  invasion  of  the 
placenta.  In  a  number  of  cases  in  which  the 
uiother  had  advanced  tuberculosis  tlie  organs  and 
blood  of  the  fetus  (stillborn  or  dying  soon  after 
birth),  contained  very  many  bacilli,  although  his- 
tologic lesions  had  not  as  yet  been  produced. 
Warthin  and  Cowie  suggest  that  the  tissue?  of  the 
fetus  may  possess  considerable  immunity  in  such 
cases.  Baumgarten  is  a  strong  believer  in  the  pos- 
sibility that  tubercle  bacilli  may  pass  to  the  fetus 
during  pregnancy  and,  remaining  latent  m  some 
of  the. tissues  (lymph  glands)  for  a  long  period, 
cause  active  tuberculosis  later  in  life.  Others  who 
are  less  radical  still  admit  that  we  should  consider 
this  as  a  possibility  (Warthin  and  Cowie,  Har- 
bitz). 
Infection  Pulmonary  tuberculosis  is  by  far  the  most  com- 
mon form  of  the  disease  in  man,  and  without  doubt 
this  is  due  to  inhalation  of  the  dried  and  pulver- 
ized sputum  of  tuberculous  patients.  Drop  infec- 
tion may  well  occur  in  the  case  of  those  who  are  in 
intimate  contact  with  the  sick.  In  kissing,  direct 
infection  from  mouth  to  mouth  is  a  dangerous 
jjossibility. 

The  reason  for  the  inception  of  pulmonary  tu- 
berculosis in  the  apex  in  so  many  cases  is  not  clear- 
ly recognized,  although  it  is  often  referred  to  the 
relative  immobility  of  this  tissue,  which  renders 
excretion  more  difficult  and  affords  improper 
aeration.  These  conditions  not  only  allow  the  or- 
ganisms to  accumulate  and  to  proliferate,  but  the 
insufficient  oxygenation  probably  causes  a  low  tis- 


TUBERCULOSIS.  419 

sue  resistance.  The  suggestion  which  has  been 
made  that  apical  tuberculosis  if  the  result  of  ex- 
tension of  the  disease  from  the  cervical  glands  does 
not  correspond  with  the  condition  seen  in  tubercu- 
losis of  adults  in  whom  the  cervical  adenitis  is 
commonly  wanting. 

The  ^'anatomic  tubercle"  is  a  primary  infection 
of  the  skin ;  lupus  vulgaris,  it  is  supposed,  may  be 
either  a  primary  infection  or  secondary  to  tubercu- 
losis in  some  other  organ;  ulcerative  tuberculosis 
is  usually  a  secondary  lesion,  often  occurring  by 
direct  extension  from  tuberculous  lymph  glands. 
Tuberculosis  of  the  nose  is  uncommon.  Infection 
of  the  tonsils  is  not  infrequent  and  probably  is  a 
common  cause  of  secondary  tuberculosis  of  the  cer- 
vical lymph  glands.  Primary  infection  of  the 
pharynx  sometimes  occurs  and  large,  coarse  granu- 
lations of  this  surface  have  been  proved  in  some 
cases  to  be  of  a  tuberculous  nature.  Tuberculosis 
of  the  pharynx  and  larynx,  however,  most  often 
arises  from  infection  with  tuberculous  sputum. 

In  the  process  of  dust  infection  of  the  lungs,  and 
also  by  other  means,  many  organisms  lodge  on  the 
mucous  membranes  of  the  nose,  mouth,  pharjTix, 
trachea  and  larger  bronchi,  but  usually  without 
producing  a  tuberculous  infection.  On  account  of 
the  movement  of  the  ciliated  epithelium,  tortuos- 
ity of  the  nasal  channels,  excretion  of  the  bacilli 
with  mucus,  the  conditions  at  these  points  are  not 
favorable  for  infection. 

Tuberculous  ulcers  of  the  esophagus  and  stom- 
ach are  very  rare,  as  is  primary  tuberculosis  of  the 
intestines.  Secondary  tuberculosis  of  the  intes- 
tines usually  is  caused  by  the  infected  sputum 


420  INFECTION   AND    IMMUNITY. 

which  tlie  patient  swallows.    Primary  infection  of 
the  genital  organs  may  arise  from  direct  contact. 

That  tubercle  bacilli  have  often  been  found  on 
the  hands  and  finger  nails  of  the  sick  as  well  as  on 
those  who  are  intimately  associated  with  them  is  a 
significant  fact  in  relation  to  the  possibility  of  in- 
fection by  direct  contact. 
Metastases.  From  a  given  focus  tubercle  bacilli  extend  to 
other  structures  in  several  ways.  On  more  or  less 
theoretical  grounds  one  speaks  of  "extension  by 
growth^'  of  the  organism  into  contiguous  tissues. 
The  commonest  method  of  extension,  however,  is 
that  of  metastasis  by  way  of  the  lymph  channels. 
When  bacilli  penetrate  a  surface,  with  or  without 
the  formation  of  a  lesion  at  the  point  of  entrance, 
as  in  the  mouth  cavity,  intestinal  canal,  or  bron- 
chial surface,  they  are  carried  to  the  lymph  glands 
of  the  region  in  which  the  tuberculous  process  is 
instituted.  As  in  plague,  the  infection  atrium  at 
times  is  indicated  by  the  set  of  glands  which  is  in- 
volved. In  certain  localities  the  secondary  invasion 
of  other  structures  takes  place  directly  without  the 
intermediate  involvement  of  lymph  glands,  as  in 
tuberculous  meningitis  caused  by  extension  from 
the  middle  ear,  and  tuberculous  peritonitis  or  peri- 
carditis by  extension  from  the  pleura.  A^ery  fre- 
quently tuberculosis  of  the  lymph  glands  and  other 
tissues  heals  spontaneously,  as  described  below.  In 
case  such  healing  does  not  occur,  metastases  con- 
tinue from  one  lymph  gland  to  another  and  to  new 
sets  of  glands  until  the  larger  lymph  channels  are 
reached,  as  a  consequence  of  which  extensive  re- 
gional or  general  tuberculosis  results.  Accidental 
localization  of  a  focus  often  causes  a  wide  depart- 
ure from  the  slow  development  Just  described.  Not 


TUBERCULOSIH.  421 

infrequently  tuberculosis  in  a  lymph  gland,  which 
is  contiguous  to  a  large  lymph  channel,  as  the  tho- 
racic duct,  invades  the  wall  of  the  latter,  the  sur- 
face softens  from  caseation  or  liquefaction  and  the 
contents,  impregnated  with  coimtless  bacilli,  are 
gradually  thrown  into  the  circulation.  Miliary 
tuberculosis,  first  of  the  lungs  and  then  of  other 
tissues,  through  the  arterial  circulation,  follows 
such  an  accident.  A  similar  course  with  variations 
ill  localization,  follows  invasion  of  the  walls  of 
branches  of  the  pulmonary  artery  or  vein.  Eup- 
ture  of  a  focus  into  a  bronchus  is  followed  by  re- 
gional or  more  extensive  dissemination  of  the  ba- 
cilli throughout  the  lungs  by  respiratory  forces. 
A  sloAver  eccentric  extension  is  seen,  particularly 
in  the  lungs,  in  which  smaller  and  larger  areas  of 
consolidation  occur.  By  means  of  short  lymphatic 
metastases  into  contiguous  territory  new  foci  are 
instituted,  which  eventually  fuse  with  the  original 
lesion.  It  is  suggested  and  generally  believed  that 
bacilli  may  be  carried  longer  or  shorter  distances 
by  wandering  phagocytic  cells.  When  tuberculosis 
once  involves  a  surface  like  that  of  the  pleura,  peri- 
toneum, pericardium  or  pelvis  of  the  kidney,  the 
whole  surface  frequently  becomes  involved  in 
thickly  studded  miliary  tubercles.  It  is  probable 
that  a  great  deal  of  dissemination  is  accomplished 
by  the  movements  of  the  fluids  and  the  surfaces  of 
these  cavities.  In  other  instances,  as  in  the  ure- 
ters. Fallopian  tubes  and  spermatic  cords,  exten- 
sion seems  to  occur  in  the  submucous  tissue  by 
means  of  the  lymphatics.  The  autopsy  often  dis- 
closes that  tuberculosis  which  appeared  to  be  "pri- 
mary^' in  such  organs  as  bones,  suprarenal  glands, 
and  meninges  was  preceded  by  an  old  process  in  a 


422  IXFKCTIOX    AM>    niMUMTY. 

l3-inph  gland  from  wliirli  metastases  occurred  to  the 
tissues  in  question. 
The  Tubercle  Certain  auatoiuic  conditions  produced  in  tuber- 
"■e  chlnqM!  culosis  wliicli  are  associated  with  recovery  from  the 
disease,  or  the  contrary,  may  be  referred  to.  The 
tubercle,  the  histologic  unit  of  the  tuberculous 
process,  is  produced  as  follows,  according  to  the 
interpretations  of  Baumgarten:  When  a  bacillus 
reaches  a  lymph  gland,  for  example,  it  multiplies 
slowly  and,  partly  through  its  presence  as  a  foreign 
body,  but  particularly  through  its  toxic  secretions, 
injures  the  surrounding  connective  tissue  and  en- 
dothelial cells  to  a  certain  degree.  Under  some 
circumstances,  especially  in  the  parenchymatous 
organs  and  lymph  glands,  this  injury  may  be  so 
gTeat  as  to  cause  the  death  of  the  adjacent  cells 
(focal  necrosis).  When  it  is  of  a  lower  order  the 
connective  tissue  and  endothelial  cells  respond  to 
the  stimulus  by  dividing  raitotically  and  eventu- 
ally accumulate  in  large  numbers  within  a  limited 
area  surrounding  the  micro-organisms.  Not  only 
the  endothelial  cells  of  the  lymph  spaces,  but  also 
those  of  the  adjacent  blood  vessels,  take  part  in 
the  proliferation,  many  of  the  vessels  being  obliter- 
ated in  consequence.  ISTot  infrequently  bacilli  are 
ingested  by  the  new  cells,  although  the  ability  of 
the  latter  to  destroy  the  organisms  is  not  clearly 
established.  Metchnikoff  saj^s  that  tubercle  bacilli 
may  remain  intracellular  for  many  months  and, 
although  not  killed,  the  pathogenicity  is  decreased 
or  destroyed.  The  new  cells  are  of  polygonal  shape, 
are  fairly  rich  in  cytoplasm,  contain  large  vesicular 
nuclei  and  are  termed  "epitheloid"  cells. 

Certain  of  the  epitheloid  cells,  usually  those  in 
.     the  center  of  the  tubercle,  where  the  bacilli  are 


TUBERCULOSIS. 


423 


most  numerous,  undergo  atypical  proliferation  in 
that  repeated  nuclear  division  takes  place  without 
corresponding  division  of  the  cytoplasm.  This 
process  results  in  the  formation  of  the  multinu- 
clear  giant  cell  vi'hich  is  so  characteristic  of  the 
well-developed  tubercle,  although  not  distinctive  of 
the  disease.  According  to  Weigert,  the  failure  of 
complete  cell  division  is  due  to  injury  to  the  cyto- 
plasm (partial  necrosis)  by  the  bacteria  which  the 
cell  contains.  Metchnikoff  and  others  take  a  dif- 
ferent view  of  the  formation  of  giant  cells,  con- 
sidering that  they  represent  individual  epitheloid 
cells  which  have  fused  to  form  a  multinuclear 
mass. 

Still  more  remote  from  the  center  of  the  tuber- 
cle, that  is,  surrounding  the  epitheloid  cells,  wan- 
dering lymphoid  and  plasmal  cells  accumulate. 
Certain  retrogressive  changes,  especially  necrosis 
and  caseation,  characterize  the  further  history  of 
the  tubercle,  although  these  changes  do  not  occur 
equally  early  nor  with  equal  intensity  in  all  cases. 
Necrosis  begins  in  the  center  of  the  lesion,  and  the 
view  is  often  expressed  that  the  formation  of  the 
giant  cell  is  the  first  indication  of  the  retrogressive 
change.  Cell  degenerations,  however,  with  karyor- 
rhexis  may  occur  before  giant  cells  have  formed. 
With  the  death  of  the  central  tissue  there  occurs 
sooner  or  later  the  death  of  many  of  the  bacilli  in 
this  portion  of  the  tubercle.  The  progressive  for- 
mation of  new  tissue  continues  in  the  periphery  as 
the  degenerative  changes  take  place  toward  the 
center;  the  tubercle  enlarges,  both  epitheloid  and 
the  surrounding  hanphoid  cells  increase  corre- 
spondingty,  and  new  giant  cells  form  at  the  periph- 
ery of  the  necrotic  center,  only  to  be  included  in 


Giant 
Cells. 


Retrogressive 
Changes. 


424 


iXFEcrrox  .wn  ntMUxiTY 


Formation  of    . 
Fibrous  Tissue. 


Caseation,  Cal- 
cification and 
Liquefaction. 


General  and 

Secondary 

Disturbances. 


the  degenerated  area  as  the  latter  extends.  In 
favorable  cases,  in  Avhicli  the  virulence  of  the  or- 
ganism is  low  or  the  resistance  of  the  individual 
strong,  the  tuberculous  area  is  eventuall}^  sur- 
rounded b}'  adult  fibrous  tissue  which  in  a  sense 
accomplishes  the  isolation  of-  the  infected  area. 
Without  question  such  a  capsule  of  scar  tissue  is  an 
obstacle  to  the  extension  of  the  tuberculous  proc- 
ess, whether  it  surrounds  a  nodule  in  a  lymph 
gland,  a  cold  abscess  or  a  tuberculous  sinus. 
Further  steps  in  the  healing  consist  of  caseation  of 
the  entire  area,  its  partial  or  complete  substitution 
by  connective  tissue  (tuberculous  scar),  or  partial 
impregnation  with  lime  salts  (calcification).  Not 
infrequently  the  caseous  portion  of  a  nodule  under- 
goes liquefaction,  which  some  have  referred  to  the 
action  of  proteolytic  ferments.  The  contents  of 
such  foci  finally  become  sterile.  In  the  event  that 
healing  of  this  nature  does  not  occur,  the  infection 
is  transmitted  to  other  organs  as  described  above. 

The  temperature,  loss  of  weight,  fever,  increased 
cardiac  action,  and  arteriosclerosis  which  are  seen 
in  tuberculosis  indicate  that  the  products  of  the 
bacillus  have  a  profound  effect  on  the  functions  of 
the  body,  and  produce  great  disturbances  in  meta- 
bolism, although  they  seem  to  have  no  marked  se- 
lective action  for  particular  tissues.  Many  disturb- 
ances are  secondary  to  changes  produced  in  partic- 
ular organs  and  are  not  referable  to  specific  ac- 
tion of  the  toxins,  such  as  those  which  are  conse- 
quent on  poor  oxygenation  in  pulmonary  tuberculo- 
sis, and  the  amyloid  degeneration  which  follows 
prolonged  suppurative  tuberculosis. 

Mixed  infection,  especially  with  the  streptococ- 
cus, plays  a  very  important  part  in  the  course  of 


TUBERCULOSIS. 


425 


pulmonary  tuberculosis,  especially  in  the  caseous 
and  cavernous  forms.  Staphylococci,  B.  pyocya- 
netis,  various  diplococci,  the  pneumococcus,  bacil- 
lus of  Friedlander,  diphtheria  and  pseudo-diph- 
theria bacilli,  and  the  influenza  bacillus  are  also 
found  as  secondary  organisms  in  pulmonary  tuber- 
culosis. Some  of  them  invade  the  surrounding 
healthy  tissue,  cause  lobular  consolidations,  and  in 
this  way  probably  prepare  a  favorable  soil  for 
further  extension  of  the  tuberculous  process.  They 
doubtless  hasten  the  liquefaction  of  caseated  tissue, 
a  step  in  the  formation  of  abscesses.  The  high  and 
irregular  fever  often  seen  in  advanced  tuberculosis 
is  commonly  septic  in  its  cause,  and  a  terminal 
streptococcus  septicemia  is  not  infrequent.  It  is 
evident  that  mixed  infections  may  complicate  at- 
tempts at  serum  therapy. 

The  essential  principles  in  the  prevention  of 
tuberculosis  consist  of,  first,  the  early  recognition 
of  the  disease,  so  that  the  patient  may  be  properly 
treated  and  cured,  if  possible,  with  the  result  that 
a  new  center  of  contagion  is  avoided;  second,  the 
rendering  of  well-developed  cases  harmless  by  suit- 
able isolation  and  proper  disposal  of  infected  ex- 
cretions; third,  the  disinfection  of  the  rooms, 
clothing,  linen  and  surroundings  of  tuberculous 
patients.  A  fourth  point,  the  prohibition  of  mar- 
riage among  the  tuberculous,  is  one  of  great  con- 
sequence, although  we  have  little  ground  to  hope 
for  its  realization.  A  fifth  point,  not  5'et  fully 
established,  is  the  possibility  of  universal  vaccina- 
tion against  the  disease. 

The  collection  of  infected  sputum  in  properly 
constructed  water-proof  paper  boxes,  which,  with 
their  contents,  should  be  burned  daily,  is  the  safest 


Mixed 
Infections. 


Principles  of 
Prophylaxis. 


426  INFECTION    AND    IMMUNITY. 

Disposal  method  of  disposing  of  this  material,  and  the  most 
effective  means  of  preventing  infection  of  the  pa- 
tient's surroundings.  Metallic,  glass  or  earthen- 
^vare  sputum-cups  containing  5  per  cent,  carbolic 
acid  are  serviceable,  but  must  be  subjected  to  fre- 
quent cleansing.  When  sputum  is  coltected  on  a 
handkerchief  the  latter  should  be  boiled  within 
twelve  hours  and  not  allowed  to  dry ;  that  the  hands 
of  the  patient  are  likely  to  be  contaminated  from 
the  handkerchief  is  evident.  In  coughing,  the 
handkerchief  should  be  held  to  the  mouth  to  catch 
droplets  of  sputum  and  saliva  Avhieh  are  expelled. 
The  ordinances  and  rules  which  prohibit  expecto- 
ration in  street  cars  and  other  public  places  should 
be  enforced.  When  bacilli  are  discharged  in  the 
urine  and  feces  or  in  the  pus  of  tuberculous  ab- 
scesses and  sinuses,  these  secretions  should  be  dis- 
infected by  suitable  means  (chlorid  of  lime). 
Healthy  persons  should  come  in  contact  with  the 
tuberculous  as  little  as  possible,  and  the  eating 
utensils  of  the  latter  should  be  used  by  no  one  else. 
Disinfection.  T]io  floor  of  a  rooui  whicli  is  inhabited  by  a  tuber- 
culous person  should  always  be  moistened  before  it 
is  swept,  in  order  to  avoid  stirring  up  the  dust. 
After  the  death  or  removal  of  a  patient,  the  entire 
surface  of  the  room  and  all  its  contents  should  be 
thoroughly  disinfected  by  appropriate  means.  The 
proper  disinfection  of  the  premises  which  werp 
once  occupied  by  a  consumptive  should  be  a  legal 
requirement.  Just  as  similar  procedures  are  de- 
manded in  the  case  of  smallpox  and  some  other 
contagious  diseases. 

The  special  hospital  in  which  the  indigent  tuber- 
culous may  be  properly  cared  for  and  isolated  has 


TUBERCULOSIS. 


427 


been  a  powerful  factor  in  causing  the  decrease  of 
tuberculosis  which  has  been  noted  in  many  coun- 
tries. The  removal  of  a  patient  to  such  an  institu- 
tion means  the  elimination  of  an  infected  focus 
from  the  community. 

Cold-blooded  animals  (fish,  amphibians,  rep- 
tiles), and  most  birds  are  not  highly  susceptible  to 
tuberculosis,  although  special  varieties  of  the  ba- 
cillus cause  the  disease  in  certain  of  them  under 
natural  conditions.  When  tubercle  bacilli  are  in- 
jected into  the  circulation  of  birds,  they  may  re- 
main in  the  blood  and  organs  for  months,  produc- 
ing little  or  no  tissue  change,  although  they  retain 
their  virulence  for  other  animals  (guinea-pigs). 
No  animal  exceeds  the  guinea-pig  in  its  susceptibil- 
ity to  this  disease.  Goats  and  sheep  are  fairly  re- 
sistant, and  the  same  is  probably  true  of  the  horse, 
although  its  artificial  infection  is  not  difficult. 
That  different  varieties  of  a  species  may  vary  in 
their  susceptibility  is  illustrated  by  the  field  mouse, 
which  is  highly  susceptible,  and  the  white  mouse, 
which  is  relatively  immune.  Although  similar 
variations  may  exist  among  different  races  of  men, 
they  are  not  readily  demonstrated.  The  high  sus- 
ceptibility which  appears  to  exist  among  certain 
races,  as  the  negro,  may  be  explained  in  part  by  un- 
hygienic methods  of  living,  in  which  safeguards 
against  infection  are  not  taken. 

The  discovery  of  healed  or  healing  tuberculous 
foci  in  70  to  90  per  cent,  of  all  autopsies,  in  con- 
trast to  the  15  to  20  per  cent,  of  deaths  from  tuber- 
culosis, shows  that  susceptibility  and  immunity  are 
subject  to  marked  individual  variations.  The 
ability  of  an  individual  to  overcome  a  tuberculous 
infection  is  referred  in  a  vague  way  to  an  unusual 


Susceptibility, 
and  Immunitir. 


Racial  and 
Individual 
Variations. 


428  INFECTION    AND    IMMUNITY. 

•  resistance  on  his  part;  his  defensive  powers  are 
said  to  he  strong.  Although  -we  remain  to  a  large 
extent  in  the  dark  concerning  these  defensive 
powers,  they  seem  to  rest  chiefly  in  the  ability  of 
the  tissues  to  destroy  the  bacilli;  that  is,  the  re- 
sistance is  antibacterial.  Many  bacilli  may  be  de- 
stroyed by  leucocytes  or  endothelial  cells  before 
they  are  able  to  cause  tissue  changes.  It  was  stated 
previously  that  healing  in  many  instances  depends 
on  isolation  of  the  focus  by  epithelioid,  lymphoid 
and  plasma  cells,  and  by  connective  tissue.  On 
general  grounds  we  may  assume  that  a  tissue  reac- 
tion of  this  nature  takes  place  with  greater  vigor 
and  rapidity  in  a  strong,  healthy  person  than  in 
one  of  lower  vitalit3^  Aside  from  the  qucj^tion  of 
individual  resistance,  recovery  or  progressive  infec- 
tion may  depend  on  the  smaller  or  larger  amount 
of  bacilli  which  gained  entrance  to  the  body,  as 
well  as  on  their  virulence.  Experiments  show  that 
susceptible  animals  recover  from  minute  doses, 
whereas  they  succumb  to  somewhat  larger  doses  of 
bacilli. 
Predisposing  Yarious  external  influences  increase  susceptibil- 
inftuences.  ^^^  ^^^  resistance.  Tuberculosis  is  to  no  small  de- 
gree a  disease  of  the  poor,  who  so  frequently  live 
in  an  undernourished  condition,  in  crowded,  dirty 
rooms,  with  little  sunlight  and  fresh  air.  The 
disease  is  more  common  in  the  cit}'  than  in  the 
country,  where  an  outdoor  life  is  the  rule.  Alco- 
holism, diabetes,  measles,  scarlatina,  whooping 
cough  often,  and  influenza  not  infrequently,  are 
precursors  of  tuberculosis.  Conditions  which  favor 
anemia,  as  pulmonary  stenosis  (rare),  predispose 
to  pulmonary  tuberculosis,  whereas  insufficiency  of 
the  left  heart,  accompanied  by  congestion  of  the 


TUBERCULOSIS.  429 

lungs,  is  not  often  associated  with  the  disease,  al- 
though it  has  no  influence  in  preventing  infection 
in  other  organs.  Tuberculosis  is  more  frequent 
during  the  first  two  or  three  years  of  life,  when 
children  are  so  commonly  confined,  than  from  the 
third  to  the  fifteenth  year,  when  they  live  in  the 
open  air  so  largely.  From  the  fifteenth  year  to 
middle  life  or  later  the  disease  increases  in  fre- 
quency because  of  greater  exposure  to  infection. 
Physicians  who  are  familiar  with  tuberculosis  in 
Scandinavian  countries  and  in  America  comment 
on  the  extent  to  which  tuberculosis  develops  among 
Scandinavians  after  they  come  to  this  country. 

Nothing  is  commoner  than  the  occurrence  of  -Hereditary 
several  successive  cases  of  phthisis  in  the  members  tendency." 
of  a  family,  and  the  expression,  heard  on  all  sides, 
that  "tuberculosis  is  in  the  family,"  indicates  the 
general  belief  that  a  family  tendency  may  be  trans- 
mitted from  generation  to  generation.  During 
recent  years,  however,  closer  analysis  of  the  condi- 
tions has  led  many  to  doubt  the  existence  or,  at  any 
rate,  the  importance  of  family  tendency  or  inher- 
ited predisposition,  and  to  refer  the  frequent  oc- 
currence of  tuberculosis  in  a  family  to  the  greater 
exposure  to  infection  which  is  occasioned  by  close 
contact  with  a  pre-existing  case.  Cornet,  who  has 
made  a  close  statistical  study  of  tuberculosis,  dis- 
credits entirely  the  hypothesis  of  hereditary  pre- 
disposition, and  Cornet  and  Meyer  refer  to  the 
"hahitus  plitMsicus,"  which  we  are  disposed  to 
look  on  as  an  objective  evidence  of  hereditary  ten- 
dency, as  a  result  rather  than  a  cause  of  pulmonary 
tuberculosis.  It  is  fair  to  say  that  the  development 
of  tuberculosis  in  several  members  of  a  family  is 
not  prima  facie  evidence  of  the  existence  of  a 


430  INFECTION    AX  I)    IMMUyiTY. 

family  predisposition  lor  the  disease.  Wiierc  there 
are  tubercle  bacilli  there  is  likel}^  to  be  tuberculosis, 
and  the  occurrence  of  the  infection  in  one  fur- 
nishes the  prerequisite,  that  is.  bacilli,  for  the  de- 
velopment of  the  disease  in  other  members  of  the 
family.  It  is  probable  that  the  verdict  of  family 
tendency  has  often  been  pronounced  erroneously. 
At  the  present  time,  however,  Ave  may  not  be  justi- 
fied in  considering  the  subject  a  closed  chapter. 
Concerning  It  is  the  commonly  accepted  opinion  that  recov- 
immunity.  ery  from  tuberculosis  does  not  confer  immunity  to 
subsequent  attacks.  Cornet  and  Meyer  suggest  as 
an  explanation  of  this  condition  that  the  local  le- 
sion is  so  strictly  isolated  that  a  sufficient  amount 
of  toxin  does  not  escape  into  the  circulation  to 
cause  a  general  reaction,  hence  the  formation  of  an- 
titoxin or  other  antibodies  is  impossible.  This  ex- 
planation seems  inadequate,  however,  when  we  re- 
member the  strong  antitoxic  immunity  which  de- 
velops in  tetanus  and  diphtheria  in  spite  of  the  lo- 
calization oi  the  bacteria.  The  results  of  artificial 
immunization,  in  which  iinlimited  amounts  of 
toxic  material  or  bacilli  may  be  injected  without 
the  formation  of  satisfactory  antitoxins,  seem  to 
indicate  that  the  toxic  constituents  of  the  tubercle 
bacillus  lack  the  power  of  causing  the  formation  of 
a  strong  antitoxin. 

In  opposition  to  the  prevailing  opinion,  certain 
observers  find  ground  for  the  belief  that  recovery 
from  local  tuberculosis  of  the  lymph  glands,  skin  or 
bones,  actually  does  render  the  patients  immune  to 
pulmonary  consumption  (]\Iaragliano  and  others). 
In  early  experiments  Koch  noted  that  when  tuber- 
cle bacilli  were  injected  subcutaneously  into 
guinea-pigs  which  were  suffering  from  general  tu- 


TUBERCULOSIS.  431 

berculosis,  the  subcutaneous  inoculation  remained 
as  a  local  infection  and  not  infrequently  healed 
after  sloughing.  The  general  infection  would  seem 
to  have  increased  local  resistance.  Although  other 
investigators  failed  to  duplicate  the  observation  of 
Koch,  this  result  is  said  to  have  suggested  to  him 
the  idea  of  active  immunization  as  a  cure  for  tu- 
berculosis, a  method  subsequently  practiced  by 
treatment  with  the  various  tuberculins. 

In  the  United  States,  Trudeau  and  de  Schwein-  Active 
itz,  and  in  Europe,  Koch,  Behring.  Maragliano  '"""""'"»'»"• 
and  Baumgarten,  with,  their  followers,  have  prac- 
ticed assiduously  the  artificial  immunization  of 
animals  Avith  the  tubercle  bacillus  or  various  prep- 
arations from  the  organism,  with  the  hope  of  pro- 
ducing active  immunity  to  the  disease.  Some  of 
the  procedures,  especially  those  of  Koch,  have  been 
transferred  to  man  as  curative  measures.  In  addi- 
tion to  active  immunization  of  man,  Maragliano 
especially  has  prepared  an  antituberculosis  serum, 
to  which  he  assigns  antitoxic  and  bactericidal 
properties,  and  which  he  and  others  claim  to  have 
used  with  good  results  in  the  treatment  of  tuber- 
culosis. Marmorek  also  prepares  an  "antitoxic" 
serum. 

It  has  been  shown  that  active  immunization 
may  so  increase  the  resistance  of  various  domestic 
animals  (guinea-pig,  sheep,  rabbit,  dog,  calf,  cow, 
etc.),  that  they  withstand  doses  of  bacilli  which 
are  invariably  fatal  for  control  animals.  When 
the  bactel-ial  cells  are  used  for  immunization  it  is 
customary  to  begin  treatment  either  with  killed 
bacilli,  or  with  living  cultures  which  are  naturally 
of  low  virulence,  or  the  virulence  of  which  has  been 
lost  by  prolonged  artificial  cultivation.    Eelatively 


432  INFECTION    AND    IMMUNITY. 

■  avinilcnt  strains  as  those  cultivated  from  fish, 
turtle  or  fowls,  have  been  utilized  for  the  first  in- 
jections. As  immunization  progresses  one  of  two 
processes  may  be  followed :  either  the  quantity  in- 
jected ma}^  be  increased  gradually,  as  when  killed 
or  avirulcnt  bacilli  are  used,  or  the  immunization 
having  been  begun  Avith  avirulent  living  cultures 
those  of  higher  virulence  may  be  substituted  later. 
In  any  case  immunization  is  difficult  and  slow, 
and  many  animals  may  be  lost  from  cachexia  or 
from  tuberculosis  which  develops  from  hasty  pro- 
gression in  dosage.  The  subcutaneous  injection 
of  intact  cells  has  the  disadvantage  that  local  ab- 
scesses frequently  develop,  and  to  avoid  this  the 
intravenous  injection  of  smaller  doses  has  been 
practiced  in  some  instances.  For  active  immuniza- 
tion the  "new  tuberculin"  of  Koch  containing  all 
the  cellular  constituents  in  a  finely  divided  form 
has  the  advantages  that  it  may  be  given  subcu- 
taneously  without  abscess  formation  and  is  ab- 
sorbed with  some  rapidity.  An  animal  or  person 
immunized  with  TK  is  immune  to  all  the  constitu- 
ents of  the  bacillus.  The  condition  produced  by 
active  immunization  is  one  of  increased  resistance 
rather  than  of  absolute  immunity;  large  doses  of 
bacilli  may  cause  infection.  The  nature  of  the 
new  resistance  is  not  satisfactorily  established. 
Tuberculin       Inasmucli  as  tubcrculin  is  used  not  only  for 

in  Diagnosis.     -, .  •      i      i       i         >>  i  ■  • 

diagnosis  but  also  for  curative  purposes  m  man 
(active  immunization),  and  since  the  principles  of 
action  are  similar  in  both  instances,  the  use  of 
tuberculin  may  be  considered  at  this  point.  A 
healthy  man  is  not  susceptible  to  moderate  doses, 
but  a  tuberculous  man  is  even  more  susceptible 
to    the    toxin    than    the    tuberculous    guinela-pig. 


TVBERCULOHIH.  433 

since  0.001  c.c.  oL'tcn  causes  an  intense  reaction, 
E.  Weigert  classifies  the  disturbances  which  tuber- 
culin may  produce  in  the  tuberculous  as  thermal, 
circulatory,  respiratory,  digestive,  nervous  and 
vasomotor,  and  secretory.  Necrosis  may  be  pro- 
duced at  the  point  of  injection.  In  so  far  as  the  di- 
agnostic use  of  tuberculin  is  concerned,  we  are  in- 
terested chiefly  in  the  thermal  disturbances, 
which  are  accompanied  by  chills,  malaise  and 
muscular  pains.  Following  injection  of  a  suitable 
quantity,  a  period  of  incubation  of  from  eight  to 
fourteen  hours  follows,  and  at  the  end  of  this  time 
the  temperature  rises  progressively  for  two  or 
more  hours  and  may  reach  a  maximum  of  from  40° 
to  41°  C;  after  remaining  at  this  point  for  from 
two  to  six  hours,  it  recedes  rapidty.  In  addition 
to  this  general  reaction,  the  toxin  causes  conges- 
tion, redness  and  swelling  at  the  site  of  the  tuber- 
culous lesions,  i.  e.,  the  foci  become  surrounded  by 
an  inflammatory  reaction.  This  is  seetn  most 
readily  in  the  tubercles  of  lupus  vulgaris,  and  in 
the  lungs  declares  itself  by  an  increase  in  rales 
and  expectoration,  caused  by  the  exudation  ac- 
companying the  inflammatory  reaction. 

For  diagnostic  purposes  the  technic  of  adminis- 
tration is  as  follows:  It  must  first  be  assuredi 
that  the  patient  has  no  continued  fever  by  noting 
the  temperature  every  two  hours  for  several  days. 
One  milligram  of  tuberculin  is  injected  subcu- 
taneousty,  this  amount  being  obtained  by  suitable' 
dilution  of  the  original  solution.  If  no  tempera- 
ture is  produced  by  this  amount,  5  or  10  mg.  may 
be  given  in  a  second  injection  after  an  interval  of 
two  or  three  days.  When  the  quantity  is  determined 
which  causes  a  rise  in  temperature  of  one-half 


434  IXFKCTIOX    AXO    /.I/ l/C'-Y/'/T. 

degree  C.  or  more,  tlie  dose  is  to  bo  repenti'd  after 
the  temperature  produced  by  the  first  injeelioii  has 
subsided.  Two  positive  reactions  should  be  con- 
sidered necessary-  for  the  diagnosis  of  tuberculo- 
sis. One  who,  after  injection  of  10  mg.  on  two 
different  occasions,  gives  no  reaction  is  to  be  con- 
sidered free  from  the  disease  (Marx). 
Limitations  in  Experience  has  taught  certain  limitations  to  the 
of  Tuberculin,  diagnostic  value  of  tuberculin:  1.  The  test  can 
not  be  applied  to  febrile  cases  inasmuch  as  the 
l^re-existing  fever  could  not  be  separated  from  that 
which  the  tuberculin  might  produce.  2.  Cases  of 
advanced  tuberculosis  frequently  fail  to  give  the 
reaction.  The  tissues  of  such  patients  have  be- 
come resistant  to  the  poison.  3.  It  is  said  that 
tuberculin  frequently  causes  a  similar  reaction  in 
those  suffering  from  lepros}',  actinomycosis  and 
svphilis.  Cornet  and  Meyer  suggest  that  the 
phenomenon  as  it  occurs  in  leprosy  and  actinomy- 
cosis is  to  be  considered  in  the  nature  of  a  "group 
reaction"  in  view  of  the  close  relationship  of  the 
tubercle  bacillus  to  actinomycee  and  Bacillus  leprcB 
It  does  not  always  occur  in  syphilis,  and  in  posi- 
tive cases  a  latent  tuberculosis  may  be  responsible 
for  the  reaction.  By  a  number  of  writers  the  facts 
just  stated  are  taken  to  indicate  that  the  reaction  is 
not  of  specific  character;  that  it  may  often  be  ob- 
tained in  the  tuberculous  by  the  injection  of  ap- 
parently indifferent  substances  as  trypsin,  peptone 
(albumose),  sodium  cinnimate  and  the  "mycopro- 
teins"  of  other  bacteria  provides  additional  sup- 
port to  this  view.  On  the  other  hand,  since  rela- 
tively large  amounts  of  these  indifferent  sub- 
stances are  required  to  produce  the  reaction,  where- 
as minute   amounts  of  tuberculin   suffice,   others 


TUBERCULOSIS.  435 

hold  that  the  specificity  of  the   latter  substance 
may  be  maintained. 

Early  tuberculosis  reacts  to  tuberculin  in  the 
most  typical  manner.  On  account  of  the  fact  that 
latent  or  healing  cases  may  respond  to  the  test,  its 
positive  outcome  gives  no  indication  of  the  serious- 
ness of  the  patient's  condition,  which  is  a  practical 
question  of  some  importance. 

The  fear  that  tuberculin,  in  producing  an  in-  Danger  f?) 
fiammatory  reaction  around  tuberculous  areas,  Tuberculin. 
may  cause  a  dissemination  of  the  bacilli,  has  acted 
strongly  in  preventing  the  use  of  the  toxin  for 
both  diagnostic  and  therapeutic  purposes.  On  a 
priori  grounds,  such  an  event  would  seem  to  be  a 
possibility,  for,  with  the  inflammation,  the  vessels 
surrounding  the  tubercles  become  congested,  new 
leucocytes  accumulate  and  there  is  an  extravasation 
of  fluid.  Since  during  the  subsidence  of  the  in- 
flammation a  certain  number  of  leucocytes  may 
again  leave  the  area  and  as  the  extravasated  fluid 
returns  to  the  circulation,  bacilli  may  be  carried  to 
other  tissues  by  them.  Contrary  to  such  reasoning, 
however,  the  observations  of  Koch  and  his  follow- 
ers in  animal  experiments  and  in  the  diagnostic 
and  therapeutic  use  of  tuberculin  in  man,  lead 
them  to  say  that  tuberculin  when  properly  ad- 
ministered never  causes  an  aggravation  or  exten- 
sion of  the  disease.  Similar  conclusions  were 
reached  by  Trudeau,  Baldwdn  and  Kinghorn  in 
animal  experiments  in  which,  "as  in  previous  ob- 
servations, a  favorable  absorptive  influence  was 
noted  on  the  diseased  focus."  Bearing  in  mind 
the  limitations  mentioned  above,  and  the  possibil- 
ity of  the  reaction  being  induced  by  leprosy,  acti- 
nomycosis and  syphilis  (  ?),  the  statement  of  Osier 


430  IXl-ECTWN    A\n    IMMUXITY. 

may  bo  quototl  that  "iu  obscure  internal  lesions, 
in  joint  cases  and  in  suspected  tuberculosis  of  the 
kidneys  the  use  of  tuberculin  gives  most  valuable 
information"' 
Tuberculin  The  Original  unfavorable  results  "which  were  ob- 
tained in  the  therapeutic  administration  of  tuber- 
culin are  referred  by  Ivoch,  Petruschky  and  others 
to  improper  selection  of  cases.  Those  in  a  febrile 
condition  and  those  in  whom  destruction  of  tissue 
is  advanced  are  not  suited  for  the  treatment,  and 
in  them  little  or  nothing  is  to  be  hoped  from  the 
administration  of  tuberculin.  Its  curative  value  is 
supposed  to  depend  on  the  local  inflammatory  reac- 
tion which  it  causes  around  tuberculous  foci,  and 
perhaps  also  on  the  necrosis  Avhich  Koch  claims  is 
caused  in  the  tubercles  themselves.  It  must  be  the 
object  during  the  whole  course  of  treatment  to  ad- 
minister the  toxin  in  such  doses  that  a  moderate 
or  minimum  local  reaction  occurs.  Larger  amounts 
which  would  cause  febrile  reactions  and  eventually 
render  the  patient  resistant  to  tuberculin  and  thus 
preclude  the  local  changes  are  to  be  avoided.  It  is 
customary  to  begin  with  1/10  to  1/20  milligram 
and  gradually  to  increase  the  amount  injected. 
If  fever  is  caused  by  a  particular  dose,  larger 
amounts  are  not  to  be  given  until  fever  ceases  to 
follow  this  dose.  By  the  time  a  dosage  of  50  milli- 
grams is  reached,  which  may  require  many  months, 
the  patient  usually  has  lost  the  power  of  reacting 
and  the  injections  are  to  be  interrupted  until  he 
again  becomes  sensitive  to  the  toxin  (from  tliree 
to  six  montlis),  after  Avhich  treatment  should  be 
resumed.  Cure  is  recognized  when  the  patient  has 
lost  permanently  the  power  to  react,  his  condition 
then  being  identical  with  that  of  the  healthy  man. 


TUBERCULOBIH.  437 

ISTimierous  German  writers  on  the  basis  of  practi- 
cal experience  assign  an  unquestionable  curative 
power  to  tuberculin  when  administered  as  de- 
scribed.   Its  use  has  not  extended  widely. 

The  principles  on  wdiich  the  action  of  tuberculin 
depend  are  hypothetical.  Marmorek  says  that  the 
fever  and  local  changes  are  due  to  a  special  toxin 
(the  true  toxin),  which  the  bacillus  secretes  under 
the  stimulation  of  the  tuberculin.  Ehrlich  sup- 
poses that  cells  adjacent  to  the  tubercles  have  been 
injured  moderately  by  the  tuberculin  which  is  pro- 
duced in  situ,  and  that  as  a  consequence  of  this 
injury  such  cells  are  particularly  susceptible  to  the 
additional  tuberculin  which  is  injected,  and  react 
to  the  stimulus  by  proliferation  (Marx).  In  ac- 
cordance with  this  conception  the  fever  also  in 
some  obscure  way  is  related  to  the  local  reaction. 
Investigations  are  needed  to  clear  up  this  point. 

In -active  immunization  with  TE,  in  which  the  Treatment  with 
solid  constituents  of  the  bacilli  are  injected  rather  lub^rcuiin^.*^' 
than  the  toxic  tuberculin,  the  cure  is  supposed  to 
depend  on  the  development  of  immune  bodies 
rather  than  on  local  tissue  changes.  Koch  pub- 
lished favorable  results  from  its  use,  but  reports 
from  other  sources  were  less  satisfactory.  Koch's 
Neuiuherculin  (BaziUenemidsion)  is  used  in  a 
similar  manner.  Koch  proposes  to  use  the  agglu- 
tinating power  of  the  patient's  serum  as  an  index 
of  the  immunity  caused  by  the  injection.  The  for- 
mation of  agglutinins  perhaps  indicates  in  a  gen- 
eral way  the  ability  of  the  patient  to  form  anti- 
bodies, but  from  the  well-known  fact  that  the  ag- 
glutinating power  does  not  go  hand  in  hand  with 
the  protective  power  of  serum  in  relation  to  many 
infections,  this  method  of  estimatins:  the  degree 


438  iyri:cTio\  axd  immvxity. 

•of  iinmunity  does  not  rest  ou  a  good  basis.  The 
aggluiination  reaction  is  carried  on  with  the  emul- 
sion which  is  used  for  immunization.  Treatment 
in  man  is  begun  by  the  injection  of  0.0025  mg.  of 
solid  substance  and  the  amount  is  increased  rap- 
idly every  day  or  two  until  a  reaction  occurs  with 
a  temperature  of  from  1.5°  to  2°  C.  After  a  pause 
of  a  week  the  injections  are  begun  again  and  event- 
ually a  dose  of  20  nig.  may  be  given.  During 
treatment  the  agglutinating  power  of  the  patient's 
serum  is  tested  frequently,  and  if  it  is  not  suffi- 
ciently high  intravenous  injection  of  the  fluid  por- 
tion of  the  emulsion  may  be  practiced.  The  agglu- 
tinating power  may  go  as  high  as  from  1  to  25  to 
1  to  150,  rarely  1  to  200  or  300. 

With  both  TR  and  the  last  preparation  animals 
may  be  successfully  immuni/^ed  against  tul)ercu- 
losis. 
Serum  of  Maragliauo  publishes  the  following  conclusions. 
^'1.  that  it  is  possible  to  produce  a  specific  (serum) 
therapy  for  tuberculosis;  2,  that  it  is  possible  to 
immunize  the  animal  organism  against  tuberculo- 
sis as  is  done  in  other  infectious  diseases,  and  that 
there  is  good  reason  for  hope  for  an  antitubercu- 
losis vaccination  for  man."  He  recognizes  bacteri- 
cidal, antitoxic  and  agglutinating  properties  of  the 
serum  as  nornuil  defensive  powers  of  the  body,  and 
says  that  these  powers  are  increased  as  the  result 
of  immunization.  The  bactericidal  power  of  the 
serum  is  determined  by  its  ability  to  inhibit  the 
growth  of  cultures  of  the  tubercle  bacillus;  its 
antitoxic  power  by  its  ability  to  neutralize  a  test 
poison  which  is  olitained  from  cultures  by  macerat- 
ing them  in  hot  water;  and  its  agglutinating 
power,  is  tested  with  tlie  homogeneous  cultures  of 


Maragliano. 


TUBERCULOHIH.  439 

Courmont  and  Aiioing.  For  the  immunization  of 
animals  a  soluble  toxin  prepared  by  the  filtration 
of  young  cultures,  and  also  the  intracellular  toxins 
•which  are  extracted  by  Avatcr  from  killed  virulent 
bacilli,  are  injected.  By  using  both  substances, 
antitoxic  and  other  antiljodies  arc  said  to  be 
formed. 

The  unusual  claim  is  made  by  Maragliano  that 
his  antituberculosis  serum  is  effective  in  the  treat- 
ment of  human  tuberculosis  not  only  because  of  its 
own  properties,  but  because  it  causi3s  the  tissues  to 
form  additional  antibodies.  It  is  difficult  to  take 
the  latter  claim  seriously,  since  it  is  not  in  accord 
with  the  laws  of  anti-body  formation  as  we  under- 
stand them  at  the  present  time.  However,  favor- 
able reports  of  the  value  of  the  serum  have  been 
published  principally  from  Italian  sources.  It  is 
claimed  that  the  serum  manifests  its  curative  pow- 
ers and  causes  an  increase  in  specific  antibodies 
when  given  per  os. 

Maragliano  also  advocates  a  method  of  mixed  Mixed  immun- 
active  and  passive  immunization  in  man,  in  which  vacdnat?on. 
a  cubic  centimeter  of  serum  is  given  subcuta- 
neously  every  second  day  for  twenty  days;  for  a 
second  period  the  same  quantity  of  serum  is  given, 
but  supplemented  by  increasing  amounts  of  the 
toxic  extract  of  bacilli ;  and  for  a  third  period  the 
toxic  extract  is  injected  in  increasing  doses  during 
from  three  to  four  months. 

The  same  authority  thinks  it  may  be  possible  to 
vaccinate  against  tuberculosis  by  a  single  subcuta- 
neous injection  of  a  vaccine  (killed  bacilli?).  He 
states  that  in  both  man  and  animals  antibodies  are 
formed  in  the  serum  following  the  vaccination,  and 
that  in  animals  their  resistance  to  infections  with 


440 


INFECTION    AND   IMMUNITY. 


Serum  of 
Marmorek. 


Immunization 
by  Milk. 


living  bacilli  is  increased.  ]\Iarmorck  asserts  that 
killed  tubercle  bacilli  which  have  been  treated  with 
his  antitoxic  serum  are  readily  absorbed  from  the 
subcutaneous  tissue,  and  proposes  the  use  of  such 
bacilli  as  a  vaccine. 

As  stated  above,  Marmorek  discredits  tuberculin 
as  the  specific  toxin  of  the  bacillus.  His  "true'' 
toxin  is  prepared  by  growing  young  and  virulent 
bacilli  ('"primitive"  bacilli)  in  a  medium  which 
contains  leucotpxic  serum,  liver  extract,  glycerin 
and  bouillon.  The  leucotoxic  serum  is  prepared 
by  immunizing  calves  with  the  leucocytes  of 
guinea-pigs.  Theoretical  considerations  which  we 
need  not  detail  suggested  the  use  of  this  medium. 
The  cultures  are  filtered  after  a  few  days  of  growth 
and  the  formation  of  tuberculin  is  avoided  as  much 
as  possible.  The  immunization  of  horses  with  this 
filtered  toxin  yields  the  antitoxic  serum  of  Mar- 
morek. Conflicting  reports  concerning  its  value 
are  published  from  French  sources.  Schwartz  an- 
nounces the  complete  cure  of  a  case  of  tuberculosis 
of  the  larynx,  and  another  of  virulent  tuberculosis 
of  the  conjunctiva  and  cornea  by  the  exclusive  use 
of  Marmorek's  serum. 

Both  Maragliano  and  Behring  aflSrm  that  the 
immunizing  subst-ances  are  excreted  in  the  milk  of 
cows  which  have  been  strongly  immunized  against 
tuberculosis,  and  both  have  suggested  that  the  use 
of  such  milk  by  infants  may  render  them  more  re- 
sistant to  tuberculosis. 

The  agglutination  reaction  has  been  suggested 
by  Courmont  and  Arloing  and  others  as  a  means  of 
diagnosis  in  tuberculosis.  Others  who  criticise  this 
idea  affirm  that  agglutinins  are  not  developed  suf- 
ficiently   in    tuberculosis    to    render   the    test    of 


TUBERCULOBIH.  441 

value,  and  that  tlic  scrum  of  normal  man  may  l>e 
as  liiglily  agglutinating  as  that  of  the  tuberculous. 
In  view  of  the  fact  that  the  tubercle  bacillus  grow? 
in  coherent  masses  in  ordinary  cultures  special 
manipulations  are  necessary  to  render  it  suitable 
for  the  agglutination  reaction.  Courmont  and  Ar- 
loing  prepare  a  homogeneous  culture  by  first  grow- 
ing the  organism  on  a  certain  potato  medium  and 
.then  in  glycerin  bouillon,  which  is  frequently 
shaken.  The  cells  are  said  to  be  well  isolated  after 
this  procedure.  Koch  uses  his  emulsion  of  pow- 
dered bacilli  for  the  test.  The  serum  of  man  or 
animals  as  a  result  of  immunization  may  reach  an 
agglutinating  power  of  1  to  2,000  exceptionally 
(Maragliano). 

APPENDIX. 

TUBERCULOSIS  AND  PSEUDOTUBERCULOSIS  IN  ANIMALS. 

Certain  differences  between  the  bacilli  of  human  and  Bovine 
bovine  tuberculosis  were  mentioned  in  the  preceding  Tuberculosis. 
section.  In  cattle  the  disease  shows  a  characteristic 
tendency  to  remain  localized  in  one  organ  or  group  of 
organs  over  a  long  period.  It  is  a  nodular  disease  as  in 
man,  but  differs  from  human  tuberculosis  in  that  no- 
dules often  grow  to  large  size,  may  be  imbedded  in  and 
sharply  differentiated  from  surrounding  healthy  tissue, 
and  not  infrequently  involve  serous  surfaces,  forming 
large  masses  of  firm  sessile  or  pedunculated  tumors. 
The  nodules  frequently  are  fibrovis  from  the  beginning, 
undergo  early  and  extensive  calcification  and  rarely 
soften.  We  are  not  to  understand,  however,  that  miliary 
tuberculosis  does  not  occur  in  cattle.  Although  the 
process  in  the  lungs  is  usually  of  a  fibrous  and  large 
nodular  nature,  rapid  dissemination  with  formation  of 
many  miliary  tubercles  may  cause  the  picture  of  acute 
tuberculous  consolidation  in  a  certain  number  of  cases. 
According  to  the  statistics  of  Ostertag,  based  on  43,000 
cases  of  bovine  tuberculosis,  localization  is  as  follows: 
Lungs,  75  per  cent.;  plevira  and  peritoneum,  50  per 
cent. ;  peribronchial  glands,  60  per  cent. :  spleen,  40  per 
cent.  In  more  or  less  generalized  cases  the  lungs  are  in- 
volved in  100  per  cent,  of  the  cases;  serous  membranes, 


44-2  IXFJJCTIOX    A.\D    niMUMTY. 

90  per  cent.;  liver,  So  per  eent.j  digestive  tract,  00  per 
cent.;  spleen,  50  per  cent.;  kidneys,  ."50  per  cent.;  mouth 
cavity,  5  per  cent.  In  cows  the  uterus,  in  general  infec- 
tion, is  involved  in  05  per  cent,  of  the  cases,  the  udders 
in  from  5  to  10  per  cent.,  and  the  ovaries  in  5  i)er  cent. 
It  seems  tliat  the  lungs  are  tlie  most  connnon  infection 
atrium,  and  transmission  probably  is  accomplished  chief- 
ly through  the  secretions  of  the  respiratory  passages. 
In  the  udders  the  process  may  at  first  be  one  of  miliary 
tuberculosis,  but  a  large  amount  of  tibrous  tissue  forms 
in  time,  numy  acini  are  transformed  into  retention  cysts, 
in  which  tubercle  bacilli,  free  or  intracellular,  may  be 
present  in  large  numbers. 

Aside  from  anatomic  changes  and  clinical  symptoms, 
diagnosis  depends  on  the  tuberculin  reaction,  and,  in 
relation  to  the  udder,  the  demonstration  of  bacilli  in  the 
milk  by  staining  methods  or  inoculation  into  guinea- 
pigs. 

The  tuberculin  reaction  in  cattle  is  similar  to  that  in 
man  and  is  subject  to  the  same  general  limitations,  but 
is  used  extensively  with  the  most  satisfactory  results. 
The  complete  elimination  of  tuberculosis  from  herds  of 
cattle  is  possible,  by  using  tuberculin  as  a  diagnostic 
test,  the  slaughtering  of  infected  animals,  and  the  dis- 
infection of  stalls. 

Tuberculosis  among  sheep  and  goats  is  rare.  It  occurs 
occasionally  in  tlie  liorse,  hog  and  dog,  and  with  more 
frequency  in  the  cat. 
Avian  ^^  form  of  tuberculosis  is  very  common  in  the  chicken, 
Tuberculosis,  and  attacks  also  the  pheasant,  dove  and  turkey.  The 
duck  and  goose  are  exempt  from  it.  Altliough  the  or- 
ganism resembles  that  of  human  tuberculosis  in  size, 
staining  properties  and  other  general  characteristics, 
differentiation  is  accomplished  by  means  of  the  follow- 
ing points:  1.  The  avian  bacillus  shows  a  greater  tend- 
ency to  pleomorphinism  as  shown  by  club-shaped  forms, 
unstained  vacuoles,  "spore-like"  bodies,  and  branching 
threads.  2.  It  has  a  greater  affinity  for  aqueous  anilin 
dyes.  3.  Growth  takes  place  in  artificial  media  more 
rapidly  and  on  solid  surfaces  is  characterized  by  its 
moist  appearance  and  mucus-like  consistence  in  contrast 
to  the  dry,  warty,  brittle  growth  of  the  human  bacillus. 
4.  The  optimum  temperature  for  gi'owth  (from  40°  to  45" 
C. )  is  several  degrees  higher  than  that  of  the  mamma- 
lian organism.  5.  Its  pathogenicity  for  guinea-pigs  is 
less  and  for  rabbits  greater  than  that  of  the  human  and 
bovine  bacilli.  Their  difference  in  pathogenicity  is 
further  shown  by  the  difficulty  which  is  met  in  trying  to 


l'Si:iJD<)TUHi:h'(JUL(),ShS. 


44:i 


infect  fowls  with  the  human  bacillus.  By  varying  tlie 
conditions  of  cultivation  and  by  animal  passage  the  two 
may  be  made  to  resemble  each  other  very  closely,  al- 
though the  permanent  transformation  of  the  human  into 
the  avian,  or  vice  versa,  has  not  been  accomplished. 

The  disease  attacks  especially  the  intestines,  mesen- 
tery and  liver,  in  which  are  found  hard,  yellowish-white 
nodules,  often  rich  in  lime  salts,  and  varying  in  size 
from  that  of  a  pea  to  that  of  a  walnut.  These  condi- 
tions suggest  the  intestines  as  the  infection  atrium.  The 
foci  are  rich  in  bacilli  and  histologically  show  the  es- 
sential characteristics  of  tuberculosis. 

'^Bacillus  tuberculosis  fiscium"  is  the  name  given  to 
an  acid-fast  organism  resembling  the  tubercle  bacillus 
which  was  cultivated  from  an  inflammatory  tumor  in 
the  abdominal  wall  of  a  carp.  It  grows  well  at  low  tem- 
peratures, the  optimum  being  25°  C,  is  found  in  large 
numbers  in  the  lesions  within  giant  cells,  and  is  dis- 
tinctly pathogenic  for  frogs.  Certain  authors  state  that 
the  human  bacillus  when  inoculated  into  the  frog  under- 
goes changes  in  its  cultural  and  pathogenic  characteris- 
tics, eventually  resembling  the  organism  cultivated  from 
fish. 

Similar  bacilli  have  been  cultivated  from  a  form  of 
tuberculosis  in  the  turtle  (Friedman),  and  Blindsch- 
leiche — ^blind  worm   ( Moeller ) . 

OTHER   OEGANISMS    RESEMBLING   THE    TUBERCLE    BACILLUS. 

Certain  other  organisms  of  low  pathogenicity  resemble 
the  tubercle  bacillus  in  their  acid-fast  properties,  their 
ability  to  grow  in  the  form  of  branching  threads,  and  to 
produce  tubercular  or  nodular  infections  of  a  local  na- 
ture in  animals.  They  may  be  placed  in  a  group  which 
includes  the  tubercle  bacillus. 

C.  Fraenkel,  also  Neufeld,  recognize  in  smegna  two 
acid-fast  bacilli,  -calling  one  "tuberculoid"  because  of  its 
morphologic  resemblance  to  the  tubercle  bacillus,  and  the 
other  "diphtheroid"  since  it  shows  the  pleomorphism  of 
the  diphtheria  bacillus.  One  of  these  organisms  may  be 
identical  with  the  "syphilis  bacillus"  (?)  of  Lustgarten. 
Smegma  bacilli  are  most  numerous  beneath  the  prepuce 
in  man  and  about  the  clitoris  and  \ailva  in  women. 
Their  chief  significance  lies  in  the  danger  that  they  may 
be  mistaken  for  tubercle  bacilli  in  suspected  cases  of 
genitourinary  tuberculosis.  Smegma  bacilli  may  readily 
enter  the  urethra  in  women  and  be  carried  into  the  blad- 
der during  catheterization  or  cystoscopic  examination. 
In  man  the  danger  of  bacteriologie  error  may  be  elimin- 


Tuberculosis 
of  Fish,  Etc. 


Smegma    Bacil- 
lus and  the  Ba- 
cillus of  Lust- 
garten. 


444  INFECTION  AND  IMMUNITY. 

ateil  largely  by  doansing  tlif  glans  and  carefully  irrigat- 
ing the  urethra.    Urine  which  is  then  passed  is  not  likely 
to  contain  smegma  bacilli    (Young  and  C'hurchman). 
„    ....  .  "Milk   bacilli'"   and   "butter   bacilli"   are   acid-fast   or- 

Milk,  Butter  ganisms  resembling  the  tubercle  bacillus  moriihologi- 
and  Grass,  cally.  In  injecting  milk  into  guinea-pigs  as  a  test  for 
tuberculous  contamination,  Petri  occasionally  noted,  as 
a  consequence,  a  thick  membranous  growth  which  en- 
cased the  liver  and  spleen  and  bound  the  coils  of  intes- 
tines together.  The  omentum  was  thickened,  and  this 
structure  and  the  mesenteric  lymph  glands  contained 
nodules.  In  pure  culture  the  organism  is  pathogenic  for 
guinea-pigs  only  when  given  in  large  doses,  and  may  kill 
the  animals  in  several  weeks  with  the  anatomic  changes 
noted  above.  Its  virulence  is  increased  by  the  simul- 
taneous injection  of  butter.  It  is  not  pathogenic  for 
man   (Herbert). 

Moeller  cultivated  organisms  resembling  the  tubercle 
bacillus  from  timothy  (timothy  bacillus),  from  manure, 
and  a  third  (grass  bacillus  II)  from  the  dust  of  a 
manger.  The  last  is  marked  with  great  pleomorphism, 
thread  formation  and  motility  in  young  cultures. 

The  leprosy  bacillus  and  the  B.  of  Lustgarten  which 
resemble  the  tubercle  bacillus  will  be  considered  later. 

PSEUDOTUBERCULOSIS   IN   ANIMALS. 

Although  some  of  the  organisms  described  above  are 
often  called  pseudotubercle  bacilli,  the  term  pseudo- 
tuberculosis is  now  applied  somewhat  specifically  to  a 
nodular  disease  occurring  in  rats,  mice  and  sheep  (and 
perhaps  in  other  domesticated  animals),  and  in  which 
organisms  differing  from  the  tubercle  bacillus  in  stain- 
ing and  culture  properties,  morphology  and  pathogenic- 
ity, are  found.  The  clinical  course  and  anatomic 
changes  are  similar  in  the  three  animals  mentioned,  al- 
though the  organisms  are  different.  The  lymph  glands 
near  the  infection  atrium  become  enlarged  chielly  by  a 
cellular  infiltrate  rather  than  extensive  proliferation  of 
fibrous  tissue.  The  nodules  undergo  a  soft  caseation 
very  early  and  rarely  show  calcification.  The  infection 
finds  its  way  to  other  sets  of  lymph  glands  and  may  be- 
come more  or  less  generalized  with  the  formation  of 
smaller  and  larger  sized  nodules. 
Rats  and  Pseudotuberculosis  of  rodents,  occurring  spontaneous- 
Mice.  ]y  jn  rats,  guinea-pigs,  rabbits  and  cats,  is  caused  by  an 
organism  of  considerable  pathogenicity,  and  may  occur 
in  epidemic  form  in  laboratory  animals.  Chickens  also 
may   contract  the  disease.     Intraperitoneal   inoculations 


LEPROHY. 


445 


in  guinea-pigs  are  fatal  in  a  few  days.  Spontaneous  in- 
fection takes  place  through  the  intestinal  tract,  and  re- 
gional organs  show  the  principal  changes.  The  liver  and 
spleen  contain  many  nodules  which  may  be  as  large  as 
a  hazelnut,  and  which  are  frequently  caseated  in  the  cen- 
ter. The  organism  is  called  BaciUus  pseudotuberculosis 
rodentium  or  Streptoiacillus  pseudotuberculosis  dor. 

The  disease  in  mice  is  caused  by  a  diphtheria-like  or- 
ganism called  Bacillus  pseudotuberculosis  murium  and 
is  pathogenic  especially  for  the  gray  mouse. 

A  similar  infection  in  sheep  is  of  more  importance  and  sheep. 
occurs  with  some  frequency.  It  is  called  pseudotubercu- 
losis ovis,  and  the  bacillus  has  a  corresponding  name. 
The  organism  is  supposed  to  gain  entrance  through 
wounds  in  the  feet  and  legs,  following  which  the  adja- 
cent lymph  glands  become  involved,  and  the  infection 
may  be  transferred  to  the  lungs  and  other  organs 
through  the  lymphatic  circulation.  The  lesions  are 
nodular,  of  varying  size,  usually  surrounded  by  a  fibrous 
capsule,  and  are  either  semipurulent  or  undergo  early 
caseation.     They-  may  be  found   in   all  the  visceral   or- 


gans. 
An 


organism    resembling    that    cultivated    from    the 


sheep  has  occasionally  been  found  in  nodular  conditions 
in  cattle. 

II.    LEPKOSY. 

Leprosy  existed  in  Egy]3t  in  prehistoric  times  course  of 
and  extended  to  another  land  only  when  inter-  "tension. 
course  was  established  between  the  two  countries. 
It  reached  Greece  at  about  345  B.  C,  Italy  in  the 
first  century  before  Christ,  and  from  the  latter 
country  extended  to  Germany,  France  and  Spain. 
Crusaders  returning  from  the  Orient  also  brought 
back  the  disease  in  later  times  and  eventually  all 
Europe  was  infected.  Leprosy  is  known  to  have 
existed  in  Great  Britain  in  the  tenth  century,  and 
from  that  country  it  was  carried  to  Iceland  and 
Greenland.  From  Germany  it  extended  to  the 
Scandinavian  countries,  and  from  the  latter  to 
Finland  and  Russia.  It  also  reached  Russia  from 
the  South  and  East,  and  in  the  South  it  was  at 


44(;  lXFi:CTl()\    AXn    rMMUXITY. 

one  time  called  the  Crimean  disease.  The  West 
Indie*;  and  South  America  probably  were  infected 
from  Spain,  and  through  these  channels  tiie  disease 
was  carried  to  the  southern  states.  The  leprosy  of 
the  western  states  seems  to  have  been  imported  by 
Norwegian  immigrants  chiefly.  In  1902  the 
T'nited  States  leprosy  commission  found  278  cases 
in  this  country.  One  hundred  and  eighty-six  of 
these  individuals  probably  contracted  the  disease 
in  this  country.  120  were  born  in  foreign  coun- 
tries and  14:5  were  native  l.)()iii.  The  disease  also 
extended  around  tlie  glolie  in  the  opposite  direc- 
tion, reaching  China,  Japan  and  the  East  Indian 
islands  from  India.  The  Sandwich  Islands  be- 
came infected  in  the  nineteenth  century. 

The  contagiousness  of  the  disease  appears  to 
have  been  recognized  at  a  very  early  period.  In 
636  A.  D.  leprosy  houses  were  instituted  in  Italy 
and  other  countries,  and  the  practice  of  segregat- 
ing lepers  soon  became  general.  The  hospitals 
were  called  Lazarus  houses  in  middle  Europe  and 
St.  George  houses  in  Scandinavian  countries. 
Pipin  and  Charles  the  Great  declared  marriage  be- 
tween lepers  illegal.  The  rapid  disappearance  of 
leprosy  in  middle  Europe  during  the  sixteenth 
century  is  ascrilied  largely  to  the  segregation  of 
the  patients. 
Bacillus  of  In  1872  Hansen  announced  that  small  rods, 
Leprosy,  ggj^^g^jj^gg  intracellular  and  sometimes  free,  were 
to  be  found  constantly  in  teased  preparations  of 
leprous  tissue.  These  rods,  leprosy  bacilli,  are 
now  imiversally  recognized  as  the  cause  of  the 
disease,  and  in  1879  they  were  stained  by  Neisser 
and  a  vear  later  l)v  Hansen.    The  orofanisin  ii?  non- 


LKI'ROHY.  447 

motile,  has  about  the  dimensions  of  the  tiiberclo 
bacillus,  the  same  staining  reactions,  and  fre- 
quently shows  a  beaded  appearance  (degeneration 
forms  (?)  ).  It  is  said  to  take  up  dyes  more  readily 
than  the  tubercle  bacillus,  but  the  difference  is  not 
so  great  as  to  be  distinctive.  It  stains  by  Grain's 
method. 

Success  in  cultivating  the  bacillus  has  been  re- 
ported a  number  of  times,  but  the  researches  of 
others  have  failed  to  confirm  these  successes.  Up 
to  the  present  time  it  is  probable  that  the  organism 
has  not  been  made  to  grow  in  artificial  media.  The 
resemblance  of  the  bacillus  to  other  acid-fast  organ- 
isms, which  are  not  pathogenic  for  animals,  and 
the  non-susceptibility  of  experiment  animals  to 
leprosy,  are  conditions  which  render  very  difficult 
the  identification  of  a  culture  as  that  of  the  leprosy 
bacillus.  Nicolli  is  said  to  have  produced  leprous 
nodules  in  monkeys  by  inoculating  them  with  dis- 
eased tissue. 

So  far  as  known  the  organism  has  no  natural  Dissemination. 
existence  outside  the  human  body,  and  it  is  dis- 
seminated only  by  the  secretions  of  the  diseased. 
It  is  discharged  chiefly  through  the  secretions  of 
the  nose  and  the  upper  respiratory  passages,  the 
surfaces  of  which  are  so  commonly  the  seat  of  lep- 
rous ulcers,  and  also  through  ulcerating  lesions  of 
the  skin.  Expectoration,  sneezing  and  coughing 
have  approximately  the  same  significance  for  the 
dissemination  of  leprosy  bacilli  as  of  tubercle  ba- 
cilli. However,  the  organisms  which  are  found  in 
the  sputum  and  nasal  secretions  appear  to  be 
largely  degenerated,  a  condition  which  may  lessen 
the  infectiousness  of  these  substances. 


Transmission.' 


Infection 
Atria. 


44S  IXFECTION  AXD  IMMUXITY. 

The  infoetiousuess  of  the  leprosy  bacillus  is  of  a 
low  character.  "Epidemiologic  experience  teaches 
that  infection  occurs  only  through  intimate  and 
prolonged  association  with  the  diseased,  in  which 
doubtless  uucleanliuess  plays  a  very  important 
role"'  (Gotschlich).  A  leprous  husband  eventually 
infects  his  wife,  and  the  children  of  lepers  com- 
monly develop  the  disease  early  in  life.  The  high 
percentage  of  leprosy  which  is  noted  among  the 
laundresses  of  infected  localities  indicates  that  the 
disease  may  also  be  transmitted  by  indirect  contact. 
Gotschlich  throws  some  doubt  on  the  importance 
of  dust  infection  since  so  many  of  the  bacilli  found 
in  sputum  appear  to  be  degenerated.  Nothing  is 
known  of  the  resistance  and  viability  of  the  organ- 
ism outside  the  body. 

On  account  of  the  early  appearance  and  almost 
constant  occurrence  of  leprous  lesions  in  the  nasal 
passages  Strieker  believes  that  the  latter  constitute 
the  chief  infection  atrium;  of  this  Hansen  is  not 
positive.  JSTasal  ulcers  may  be  present  in  latent 
or  apparently  healed  cases.  Kolle  cites  a  case  show- 
ing extensive  involvement  of  the  spleen  and  liver 
in  which  the  intestinal  tract  was  considered  the  in- 
fection atrium.  In  some  instances  in  which  the 
disease  is  first  noted  in  the  feet,  the  organisms 
are  supposed  to  gain  entrance  with  infected  soil 
through  abrasions  in  the  skin.  According  to  Cor- 
nil  and  Babes,  infection  may  take  place  through 
the  hair  follicles  and  sebaceous  glands.  The  theory 
of  Jonathan  Hutchinson  that  leprosy  may  be  con- 
tracted through  eating  diseased  fish,  or  that  the  lat- 
ter in  some  way  may  render  individuals  susceptible 
to  infection  is  not  now  credited.  Hereditary 
acquisition  of  the  disease  is  of  doubtful  occur- 


LEPROSY.  449 

rence,  altlioiigh  the  bacilli  have  been  found  in  ova 
(Babes)  and  commonly  are  present  in  enormous 
numbers  in  the  testicles.  Hansen  states,  however, 
that  he  has  never  found  them  in  the  female  gen- 
erative organs. 

The  presence  of  large  masses  of  bacilli  in  leprous 
tissues  is  a  characteristic  of  the  disease.  To  a  large 
extent  they  are  intracellular  and  they  are  often 
grouped  in  such  a  way  as  to  resemble  bundles  of 
cigars.  Hansen  believes  that  the  bacillus  is  essen- 
tially an  intracellular  parasite,  and  that  it  becomes 
extracellular  only  as  a  result  of  degeneration  and 
disintegration  of  infected  cells.  Unna,  on  the 
other  hand,  considers  their  location  in  lymph 
spaces  as  most  characteristic.  They  appear  to  be 
carried  to  distant  parts  through  the  lymphatics. 
Certain  large  vacuolated  cells,  the  lepra  cells  of 
Virehow,  the  glohi  of  Hansen,  which  are  filled  to 
bursting  with  the  leprosy  bacilli,  are  characteristic 
of  the  disease.  Unna  and  others  consider  these 
bodies  as  zooglear  masses  rather  than  as  intracel- 
lular accumulations,  and  Kanthack  interprets  them 
as  bacillary  thrombi  in  the  lymphatic  vessels.  The 
nodules,  or  lepromas,  consist  of  granulation  tissue, 
containing  many  roimd  and  epithelioid  cells,  lepra 
cells  and  occasional  multinuclear  giant  cells.  In 
cutaneous  macules  columns  of  round  cells  surround 
the  blood  vessels,  there  is  some  proliferation  of 
epithelioid  cells,  but .  relatively  few  bacilli.  The 
bacilli  are  most  numerous  in  the  nodular  lesions. 
They  are  found  in  the  Glissonian  tissue  of  the  liver, 
in  the  pulp  and  follicles  of  the  spleen,  in  the  glom- 
eruli and  interstitial  tissue  of  the  kidneys  when 
these  organs  are  involved,  in  the  nerves  in  both 
the  nodular  and  maculoanesthetic  forms  of  the 


Location  of 
Bacilli. 


450  IXFECTIOX    AXD    IMMUNITY. 

disease,  and  iu  the  vascular  endothelium.  They 
have  been  demonstrated  often  in  the  ganglionic 
cells  of  the  posterior  root  ganglia.  Their  occur- 
rence in  these  cells  leads  MetchnikofT  to  say  that 
the  latter  have  phagocytic  properties. 

Endotoxin  (?)  In  yiew  of  the  chronic  course  of  leprosy  and  the 
absence  of  signs  of  intoxication  over  considerable 
periods,  it  seems  probable  that  the  bacillus  secretes 
little  or  no  soluble  toxin.  From  time  to  time,  how- 
ever, patients  with  tubercular  leprosy  develop  fever, 
which  may  persist  for  weeks  or  months  and  event- 
ually terminate  in  death.  During  such  attacks 
the  nodules  not  infrequently  enlarge,  become  soft 
and  later  disappear.  Lie  conceives  that  such 
periods  represent  massive  infection  of  the  blood 
with  the  bacilli,  and  that  at  this  time  the  latter 
imdcrgo  extensive  disintegration  and  liberate  en- 
docellular  toxins  to  which  the  toxic  phenomena  are 
due.  It  is  a  remarkable  fact  that  intercurrent  in- 
fections, as  measles  and  smallpox,  and  the  adminis- 
tration of  potassium  iodid,  cause  a  similar  enlarge- 
ment, softening  and  final  disappearance  of  leprous 
nodules,  accompanied  by  marked  degenerative 
changes  in  the  bacilli.  Hansen  is  of  the  opinion 
that  the  fever  induced  by  these  conditions  has  an 
actual  curative  effect,  although  its  influence  is  not 
readily  anal5^zed.  He  quotes  the  opinion  of  Dan- 
ielssen  that  potassium  iodid  may  be  used  to  deter- 
mine the  cure  of  leprosy,  which  would  be  indicated 
by  absence  of  a  febrile  reaction. 

General  confidence  is  not  felt  in  the  "leprolin" 
which  Rost  prepared  from  his  cultures  of  the  lep- 
rosy bacillus  (?).     His  cultures  are  said  to  have 

^"amf  Means  ^^^®^  mixtures  of  micro-organisms. 
of  Defense.       Bccausc  of  the  failure  to  cultivate  the  leprosy 


LEPJtOHY.  451 

bacillus^  experimental  work  with  the  serum  and 
cells  of  man  and  animals,  by  which  conclusions 
as  to  the  defensive  powers  of  the  body  might  be 
drawn,  can  not  be  carried  out.  It  seems  probable 
that  all  men  are  susceptible  to  leprosy  under  the 
proper  conditions.  Sauton  states  that  children  of 
from  4  to  5  years  are  particularly  liable  to  infec- 
tion. Other  conditions  which  may  increase  sus- 
ceptibility are  of  a  conjectural  nature.  It  is  pos- 
sible that  leprosy  predisposes  to  tuberculous  infec- 
tion (?). 

The  condition  in  leprosy  seems  to  be  that  of  an 
organism  of  low  virulence  against  which  the  body 
possesses  no  decisive  protective  agency.  The  reac- 
tions for  the  most  part  are  of  a  local  nature,  involv- 
ing the  proliferation  of  connective  tissue  and  hlood 
vessels,  and  the  accumulation  of  lymphocytes.  That 
phagocytosis  by  macrophages  (lymphocytes,  con- 
nective tissue,  endothelial  and  ganglionic  cells)  is 
a  factor  which  antagonizes  the  proliferation  of  the 
bacilli  is  suggested  by  the  large  number  of  bacilli 
which  are  found  in  these  cells. 

The  principles  of  prophylaxis  may  be  illustrated  Prophylaxis. 
by  citing  the  practices  in  Norway.  Originally  all 
lepers  were  confined  to  institutions.  At  the  present 
time,  however,  only  indigent  lepers  and  those  who 
can  not  be  suitably  cared  for  at  home  are  required 
to  enter  an  asylum,  where  they  live  under  the  best 
hygienic  conditions.  Other  patients  are  allowed  to 
remain  at  home,  with  the  understanding  that  they 
sleep  alone  and,  if  possible,  have  separate  rooms, 
that  their  clothing,  linen  and  eating  utensils  be 
used  by  no  one  else,  and  that  proper  precautions 
be  taken  in  the  washing  of  linen.  Dressings  and 
bandages  must  be  burned.    Under  these  regulations 


452  lyFECTION    .l.YD    IMMUNITY. 

the  number  of  lepers  in  Norway  has  decreased  from 
2.8:0  in  1S5G  to  577  in  1900.  Banishmont  to  tlie 
Ishiud  of  ]\Iolokai  is  practiced  in  the  Sandwich  Is- 
hmds.  Segregation  of  lepers  should  be  brought 
about  in  this  country. 

Carasquilla  attempted  the  production  of  an  anti- 
leprosy  serum  by  immunizing  liorses  with  the  Idood 
of  leprous  patients.  Although  a  few  favorable  re- 
ports concerning  its  effects  appeared  it  has  not 
proved  of  value  in  the  hands  of  others. 

III.    GLANDERS   (FARCY). 

Occurrence  of  Under  natural  conditions  the  horse  is  the  chief 
t  e  isease.  ^^j^gj-gp  from  glanders  or  farcy,  the  former  name 
being  applied  to  the  disease  as  it  occurs  in  the  nose, 
the  latter  when  in  the  skin.  These  names  are  relics 
of  the  time  when  the  two  forms  of  the  disease  were 
not  recognized  as  having  a  common  etiology.  In 
either  locality  the  disease  may  be  acute  or  chronic, 
and  in  the  horse  about  90  per  cent,  of  the  cases 
are  chronic.  The  ass  is  occasionally  infected,  and 
in  this  animal,  as  well  as  in  man,  an  acute  general 
infection  (bacillemia)  frequently  develops,  in  ad- 
dition to  the  cutaneous  and  nasal  lesions  which 
characterize  the  disease.  Fortunately,  glanders  in 
man  is  rare.  Cows  and  rats  are  immune,  or  nearly 
so ;  the  sheep,  goat  and  dog  have  fairly  high  resis- 
tance, although  they  may  be  infected  artificially; 
the  dog  and  rabbit  are  moderately  susceptible,  and 
for  the  guinea-pig  and  members  of  the  cat  family 
(tiger,  lion  and  leopard),  the  bacillus  is  very  vir- 
ulent. Infection  of  the  last  named  animals  has 
been  noted  in  menageries  as  the  result  of  feeding 
them  with  the  meat  of  a  horse  which  had  died  of 
glanders.    The  acute  infection  usually  is  fatal,  and 


Mallei. 


GLANDERS.  453 

complete  recovery  from  the  chronic  form  of  the  dis- 
ease is  infrequent.  Something  less  tlian  50  per 
cent,  of  the  chronic  infections  in  man  terminate 
in  recovery. 

The  specific  microbe^  Bacillus  mallei,  discovered  Bacillus 
in  1882  by  Loeffler  and  Schiitz,'  is  an  aerobic  or- 
ganism which  has  approximately  the  morphology 
and  size  of  the  tul)ercle  bacillus,  but  lacks  the  acid- 
fast  property  of  the  latter.  It  stains  with  anilin 
dyes,  especially  carbol  fuchsin,  but  not  by  Gram's 
method.  With  weak  staining  it  shows  a  granular 
structure.  It  grows  well  on  ordinary  culture  media, 
showing  a  characteristic  appearance  on  potato.  In 
unfavorable  media  it  may  produce  threads,  while 
under  more  favorable  conditions  coccus-like  forms 
are  seen.  Marked  involution  forms  occur  on  media 
containing  3  per  cent,  of  sodium  chlorid 
(Wherry).  The  optimum  temperature  for  growth 
is  from  30°  to  40°  C. 

The  bacillus  is  only  moderately  susceptible  to  Resistance  and 
sunlight,  by  which  it  is  killed  in  about  twentj^-four 
hours.  It  withstands  freezing,  lives  for  two  or 
three  weeks  in  a  dried  condition  at  room  tempera- 
ture, and  is  killed  by  a  temperature  of  from  56°  to 
60°  C.  in  from  ten  minutes  to  one  and  one-half 
hours,  depending  on  the  amount  and  character  of 
the  medium  in  which  it  lies.  Its  resistance  to  the 
ordinary  disinfectants  (corrosive  sublimate,  car- 
bolic acid,  etc.),  is  not  high.  Milk  of-  lime  and 
solutions  of  calcium  chlorid  are  suitable  for  the  dis- 
infection of  stalls.  In  culture  media  the  organism 
secretes  no  soluble  toxin,  but  it  contains  an  endo- 
toxin which  probably  is  one  of  the  constituents  in 
the  various  preparations  of  mallein. 

The  method  bv  which  the  mallein  of  Eoux  and 


Endotoxin. 


4o4  INFECTION    AND    IMMUNITY. 

Preparation  XoL'urd  is  pivpurcd  is  idoiilifal  uilh  that  used  in 
the  preparation  oi'  the  old  tuberculin.  A  virulent 
strain  of  the  glanders  bacillus  is  allowed  to  grow 
for  some  time  (from  two  weeks  to  two  or  three 
months),  in  bouillon  which  contains  from  4  to  5 
per  cent,  of  glycerin,  the  culture  is  tlien  sterilized 
by  heat  and  the  bacteria  removed  by  filtration. 
The  toxin  is  not  destroyed  by  high  temperature. 
Other  preparations,  also  called  mallein,  are  made 
by  extracting  ground-up  bacilli  with  a  solution  of 
gh'cerin  and  water  (Helman,  Kalning),  or  with 
water  alone  (Kalning  and  others) ;  by  killing  a 
liquid  culture  of  the  bacillus  (Bromberg)  ;  or  by 
precipitating  bouillon  filtrates  with  absolute  alco- 
hol (de  Schweinitz  and  Kilbourne),  or  with  am- 
monium sulphate  or  magnesium  sulphate.  The 
dry  powders  "morvin"  and  "dried  mallein"  are 
prepared  by  one  or  another  of  these  precipitation 
methods. 

Distribution  Glandcrs  bacilli  are  found  only  in  the  tissues 
and  secretions  of  diseased  animals,  and  the  nasal 
discharges  of  the  latter  are  the  chief  means  of  con- 
taminating feed,  water  and  stables  through  which 
the  disease  usually  is  carried  to  other  animals. 
The  glanders  bacillus  does  not  readily  penetrate 
the  intact  skin  and  mucous  membranes,  although 
occasionally  it  may  gain  entrance  through  the  hair 
follicles  or  sweat  ducts.  In  the  presence  of  even 
slight  defects  in  these  surfaces,  as  those  caused  in 
the  mouth  or  nostrils  of  horses  by  hay  or  other 
food,  infection  readily  occurs.  According  to  No- 
card,  invasion  takes  place  commonly  through  the 
gastrointestinal  tract  following  the  ingestion  of  in- 
fected feed  or  water.  Although  involvement  of  the 
intestines  and  adjacent  tissues  frequently  results, 


of  Bacilli  and 
Infection  Atria. 


GLANDER8.  455 

the  organisms  may  become  generalized,  causing  the 
disease  in  the  nose,  skin  or  other  organs,  without 
the  establishment  of  foci  in  the  intestines. 

In  man  infection  occurs  chiefly  through  abra- 
sions in  the  skin,  and  perhaps  also  through  the 
nose,  to  which  the  bacilli  have  been  carried  by 
soiled  fingers  or  other  means.  Several  cases  of 
acute  glanders,  ending  fatally,  have  occurred  in 
laboratory  workers  as  the  result  of  accidental  in- 
oculation. There  appears  to  be  little  danger  to 
man  in  eating  the  meat  of  horses  in  which  the  dis- 
ease was  localized,  provided  the  meat  has  been  well 
cooked.  Such  meat  was  fed  to  soldiers  in  one  in- 
stance with  no  ill  results. 

Variations  in  the  course  of  the  disease  and  in  the  Tissue 
intensity  of  the  pathologic  changes  in  different 
cases  probably  depend  on  variations  in  the  resist- 
ance of  the  host  and  in  the  virulence  of  the  para- 
site. In  acute  general  infections  in  man,  follow- 
ing an  incubation  period  of  from  two  to  five  days, 
during  which  the  point  of  inoculation  becomes  vio- 
lently inflamed,  a  severe  febrile  condition  develops, 
which  is  accompanied  by  general  pains,  swollen 
joints,  a  macular  eruption,  and  often  muscular  and 
subcutaneous  abscesses.  In  a  short  time  nodules 
and  indurated  cords,  made  up  of  a  leucocytic  exu- 
date, edematous  fluid  and  proliferating  connective 
tissue  cells,  form  in  the  subcutaneous  lymphatic 
channels,  and  mark  the  progress  of  the  infection 
toward  the  lymph  glands.  The  nodules,  and  also 
the  cords,  commonly  undergo  softening,  and  ab- 
scesses form  and  rupture  through  the  skin.  Nod- 
ules similar  to  those  in  the  skin  develop  in  various 
organs  of  the  body;  in  the  nose  they  break  down 
and  constitute  ulcers.     In  chronic  infections  the 


Protective 
Processes. 


45G  INFECTION    AND    IMMUNITY. 

lesions  are  of  the  saiuc  nature,  although  they  evolve 
more  slowly  and  tend  to  remain  limited  to  particu- 
lar regions.  Xasal,  i)haryngeal.  tracheal  or  pulmon- 
ary glanders  are  forms  of  the  disease  which  are  en- 
countered in  the  horse.  Connective  tissue  develop- 
ment is  more  marked  in  chronic  than  in  acute 
glanders,  although  the  peculiar  liquefaction,  sup- 
puration and  ulceration  oL'  the  lesions  occur  in  tiie 
former  as  well  as  in  the  latter.  Moderate  Icucocy- 
tosis  is  found  in  the  blood  (12000-14000). 

The  nature  of  the  pathologic  changes  found  in 
glanders,  the  frequent  chronic  and  the  progressive 
course  of  the  disease,  and  the  fact  that  infection 
does  not  confer  distinct  immunity,  are  conditions 
whicli  ally  glanders  very  closely  to  tuberculosis, 
pseudo-tuberculosis  and  leprosy.  The  essential 
lesion  is  the  "infectious  granuloma,"  and  it  is  prob- 
able that  the  new  connective  tissue  which  is  formed 
is  to  no  small  extent  a  factor  in  limiting  the  exten- 
sion of  the  infection.  jSTodules  of  glanders  fre- 
quently are  isolated  by  the  surrounding  reaction, 
the  centers  caseate  and  the  contents  eventually  are 
discharged  through  the  skin;  cicatrization  and 
healing  in  many  lesions  follow  evacuation.  Phago- 
cytosis of  the  bacilli  by  the  epithelioid  cells  and  leu- 
cocytes in  the  nodules  is  said  to  be  rather  extensive. 
According  to  I^ocard,  there  is  no  such  thing  as  an 
acquired  immunity  to  glanders;  chronic  glanders 
may  at  any  time  become  acute.  The  cause  of  the 
natural  immunity  of  cattle  and  some  other  animals 
seems  not  to  have  been  determined. 

Treatment  of  glanders  with  immune  serums  has 
""waHein!  not  been  successful.  Such  treatment  has  been  at- 
tempted with  serum  prepared  by  immunization 
witli  mallein   (Semmer),  and  with  the  serum  of 


Serum  Therapy 


GLANDERS.  457 

diseased  animals  (Plell  and  Toeper).  The  value 
of  mallein  in  the  diagnosis  of  glanders  or  farcy  is 
similar  to  that  of  tuberculin  in  tuberculosis.  Al- 
though it  causes  a  rise  in  the  temperature  of  nor- 
mal animals  when  given  in  considerable  doses,  the 
reaction  produced  in  infected  animals  is  so  much 
more  intense,  and  occurs  with  such  smaller  doses, 
that  it  is  generally  considered  as  specific  in  nature. 
Some  doubt,  however,  has  been  thrown  on  the  spe- 
cificity of  the  reaction  from  the  facts  reported  by 
various  observers  that  toxic  substances  Irom  other 
organisms,  as  tuberculin  and  preparations  from 
the  pneumobacillus  of  Friedlander,  Bacillus 
pyocijaneus,  etc.,  cause  similar  phenomena  in  ani- 
mals suffering  from  glanders.  Wladimiroff  asserts, 
however,  that  the  reactions  caused  by  these  sub- 
stances differ  from  that  of  mallein. 

For  diagnosis  a  dose  must  be  used  which  causes 
no  reaction  in  a  normal  animal,  and  this  varies 
with  different  preparations.  The  typical  reaction 
has  two  essential  components :  1,  A  rise  in  tem- 
perature which  begins  in  from  six  to  twelve  hours 
after  the  injection,  reaches  its  maximum  (from  40° 
to  42°  C.)  in  from  six  to  eight  hours  later,  where 
it  remains  for  a  few  hours,  then  gradually  sinks, 
only  to  recur  on  the  second  day ;  3,  an  edematous 
and  inflammatory  tumor  at  the  point  of  injection, 
which  begins  in  from  six  to  eight  hours,  and  runs 
its  course  in  from  three  to  eight  days,  ending  in 
resorption  (Wladimiroff).  Veterinarians  gener- 
ally agree  that  mallein  is  a  valuable  diagnostic 
agent.  Mallein  also  has  been  used  in  the  treatment 
of  glanders,  but  with  rather  doubtful  results. 

Bacteriologic  diagnosis  is  accomplished  by  culti- 
vating the  bacilli  from  the  abscess  or  secretions  and 


458  IXFECTIOX    AND    IMMUyiTY. 

testing  the  virulence  of  the  culture  b}'  animal  ex- 
periments (guinea-pig). 
Agfliutination.  Xonual  horse  scrum  aggluiinatcs  the  glanders 
bacillus  in  dilutions  of  from  1/500  to  1/700,  that 
of  the  diseased  animal  in  a  strength  of  from 
1/1600  to  1/2000.  In  some  instances,  however, 
infection  causes  no  increase  in  the  agglutinating 
power  of  the  serum.  Agglutinins  are  said  to  be 
formed  more  readily  in  man  tlum  in  animals. 

IV.   RHINOSCLEROMA. 

(See  page  402.) 

V.   ACTINOMYCOSIS. 

Actinomycosis  is  a  chronic  infectious  disease  of 
man  and  animals,  the  lesions  of  which  present, 
characteristically,  a  central  mass  of  purulent  and 
necrotic  material  containing  colonies  of  "ray 
fungi,"  about  or  through  which  is  disposed  an 
abundant  growth  of  granulation  or  fibrous  tissue. 
In  young  or  rapidly  progressing  lesions  the  amount 
of  purulent  material  is  large,  while  in  older  lesions 
well  formed  connective  tissue  is  more  conspicuous. 
The  disease  prevails  especially  among  cattle,  al- 
though it  is  met  occasionally  in  the  horse,  hog, 
sheep,  dog,  cat  and  other  animals ;  man  is  infected 
not  infrequently. 

Although  fungous  threads  had  been  found  in 
diseases  resembling  actinomj^cosis  in  1845  and 
later,  Bollinger,  in  1877,  gave  the  first  accurate  de- 
scription of  the  disease  in  cattle,  and  in  1878  J. 
Israel  described  it  as  a  new  disease  in  man.  A 
short  time  later  Ponfick  demonstrated  the  identity 
of  bovine  and  human  actinomycosis. 

The    specific    organism,    Actinomyces    hovis    et 


•    ACTINOMYCOSIS.  459 

hominis,  on  culture  media  consists  of  a  mass  of  del-  The  runKis. 
icate  threads  which  exhibit  "true  branching"  and 
which^  to  a  certain  extent,  segment  to  form 
"spores."  The  radially  arranged  groups  of  cells 
which  occur  as  macroscopic  granules  in  the  pus  of 
the  actinomycotic  abscesses,  and  which  give  to  the 
organism  the  name  of  the  "ray  fungus,"  are  essen- 
tially a  manifestation  of  parasitic  existence, 
although  colonies  developing  on  media  which 
contain  serum  or  ascitic  fluid  may  show  a 
degree  of  "club"  formation  (Wright).  .  Each 
granule  represents  a  colony  of  organisms  the 
members  of  which  possess  club-shaped  extremi- 
ties, and  in  the  center  of  the  mass  and 
extending  from  it  are  many  of  the  delicate  threads 
found  in  cultures  of  the  organism.  It  grows  on 
various  culture  media,  often  as  a  mold,  and  stains 
by  Gram's  method. 

The  actinomyces  is  an  organism  of  considerable  Resistance. 
resistance.  Cultures  remain  alive  for  one  year  or 
more  when  in  a  dried  condition  and  the  spores  in 
one  instance  germinated  after  having  been  pre- 
served for  six  years.  A  temperature  of  80°  C. 
for  fifteen  minvites  kills  the  spores  (Berard  and 
Nicolas) .  When  suspended  in  bouillon,  spores  are 
killed  in  fifteen  hours  by  direct  sunlight,  but  when 
thoroughly  dried,  approximately  ten  days'  expos- 
ure produced  no  injury. 

Attempts  to  place  the  actinomyces  in  a  botanic 
system  have  resulted  in  many  differences  of  opin- 
ion. By  some  investigators  they  are  considered  as 
an  independent  family  midwa}^  between  the  hy- 
phomycetes  and  the  schizomycetes  (bacteria),  oth- 
ers place  them  under  the  hyphomycetes  in  the  group 


4G0 


IXFECTION    AXD    I  Mil  UN  ITT. 


Artificial 
Infection. 


Transmission 

and  Infection 

Atria. 


of  the  streptothrix.  while  still  others  consider  them 
as  pleomorphous  bacteria,  placing  them  in  the 
group  cladothrix.  Petruschky  recognizes  acti- 
nomvces.  strejitothrix,  cladothrix  and  leptothrix  as 
genera  in  the  family  trichomyces,  the  latter  belong- 
ing to  the  order  hyphomyces.  Biological  variations 
which  have  been  encountered  have  led  to  the  rec- 
ognition of  several  species  of  actinomyces,  among 
which  are  a  number  of  non-pathogenic  forms. 
Wright  limits  the  term  actinomyces  to  those  strains 
which  produce  colonies  of  club-shaped  organisms 
in  animal  tissues. 

Many  attempts  have  been  made  to  transmit 
actinomycosis  to  animals  by  inoculating  them  with 
tiie  diseased  tissues  of  animals  and  man,  and  with 
pure  cultures  obtained  from  these  tissues.  Al- 
though a  number  of  experimenters  have  reported 
positive  results,  the  attempts  usually  have  been 
fruitless.  Probably  Wright  has  been  more  success- 
ful than  others  in  producing  actinomycotic  lesions 
in  rabbits  and  guinea-pigs  by  the  inoculation  of 
pure  cultures.  Colonies  of  club-shaped  organisms 
developed  with  considerable  uniformity.  In  many 
instances  the  infection  remains  localized,  not  caus- 
ing the  progressive  and  destructive  changes  which 
actinom5^cosis  produces  when  it  occurs  naturally. 

The  organism  has  been  found  on  grains,  straws 
and  other  kinds  of  feed,  with  which  it  may  be  im- 
planted in  the  soft  parts  of  the  mouth  (gums, 
tongue),  or  in  carious  teeth.  Transmission  to  man 
by  eating  the  meat  of  actinomycotic  cattle  has  not 
been  noted.  In  man  the  disease  is  primary  in  the 
internal  organs  (lungs,  intestines,  liver,  brain, 
etc.)  in  a  large  percentage  of  the  cases,  whereas 
"lumpy  jaw"  is  rare.    The  disease  extends  locally 


ACTINOMYCOSIS. 


40 1 


by  the  gradual  involvement  of  adjacent  ti^^sues, 
which  in  time  become  occupied  by  sinuses,  ab- 
scesses and  masses  of  connective  tissue.  Numerous 
"spores"  and  bacillus-like  cells,  having  their  source 
in  the  fungous  threads,  abound  in  the  vicinity  of  a 
colony.  The  occurrence  of  such  forms  in  leuco- 
cytes and  other  large  mononuclear  cells  has  led 
some  to  the  vievs^  that  the  micro-organisms  may 
be  carried  to  neighboring  tissues  or  to  distant 
parts  as  cell  inclusions.  In  cattle  the  disease  usu- 
ally is  more  chronic  than  in  man,  more  fibrous  tis- 
sue is  formed  and  metastases  in  internal  organs 
are  less  frequent.  In  man  the  lesions  are  more 
purulent  in  character,  large  abscesses  sometimes 
form  as  in  the  liver,  and  metastases  in  visceral  or- 
gans are  more  common.  Cases  of  general  acti- 
nomycosis are  occasionally  met  with  in  both  cattle 
and  man. 

Little  can  be  said  in  the  way  of  prophylaxis  Prophyiaxi*. 
against  actinomycosis.  Knowing  the  part  that  in- 
fected grains,  straws,  etc.,  play  in  instituting  in- 
fection, the  practice  of  biting  or  chewing  grains  or 
of  using  straws  as  toothpicks,  evidently  is  one 
which  affords  opportunity  for  infection.  The  pres- 
ence of  carious  teeth  has  often  been  suggested  as 
a  predisposing  condition  for  infection. 

Practically  nothing  is  known  concerning  the  de- 
gree to  which  susceptibility  to  actinomycosis  pre- 
vails, and  the  question  of  immunity  to  the  disease 
remains  unexplored.  The  inability  to  reproduce 
the  infection  in  animals  at  will  renders  a  satisfac- 
tory study  of  these  questions  very  difficult.  The 
presence  of  large  numbers  of  pol5'morphonuclear 
leucocytes  in  the  vicinity  of  the  organisms  sug- 
gests, but  does  not  prove,  that  they  may  have  some 


Immunity  and 
Susceptibility. 


462  IXFECTIOX    AXD    IMMUMTl. 

infhieuce  in  combating  the  infection.  Surely  the 
abundant  mass  of  connective  tissue  which  develops 
about  the  abscesses  and  sinuses  aids  in  confining 
the  process  to  a  definite  region. 

That  the  iodid  of  potassium  has  a  c  ma  live  influ- 
ence on  some  cases  of  actinom3'cosis  seems  to  have 
been  well  demonstrated.  The  principles  by  which 
it  produces  its  effects  are  nnknown. 

VI.    MADURA   FOOT. 

Mycetoma.  j\Iycctoma,  or  Madura  foot,  resembles  actinomy- 
cosis in  the  formation  of  abscesses,  sinuses  and 
granulation  tissue,  but  it  shows  a  peculiar  predilec- 
tion for  the  foot,  which  probal^ly  is  explained  by 
the  greater  exposure  of  this  part  to  infection.  This 
disease  differs  from  actinomycosis  in  that  the 
course  is  more  chronic  and  it  is  never  accompanied 
by  generalized  infection.  The  bones  are  not  in- 
volved so  frequently  as  in  actinomycosis.  Granules 
similar  to  those  of  actinomycosis  are  found  in  the 
cells,  which,  however,  do  not  assume  the  pro- 
nounced club  shape  seen  in  colonies  of  the  ray  fun- 
gus. 

Two  varieties  of  the  disease  are  known,  one  in 
which  the  granules  are  brown  or  black,  and  an- 
other in  which  they  are  white  or  yellowish;  the 
latter  is  encountered  much  more  frequently  than 
the  former. 

Pure  cultures  of  the  organism,  which  is  called 
Streptothrix  madurce  (Vincent),  were  first  ob- 
tained by  Vincent  in  1894,  and  have  been  studied 
by  a  number  of  observers  since  that  time.  It  bears 
a  close  resemblance  to  the  actinomyces  and  by  some 
is  considered  a  variety  of  this  organism.  Differ- 
ences between  the  black  and  white  varieties  are  not 


OIDIOMYCOaiii.  463 

clearly  set  forth.  Tlie  disease  occurs  in  southern 
Asiatic  countries,  in  northern  Africa,  and  in  the 
United  States  (rare). 

VII.    INFECTIONS     BY     STREPTOTHRIX,     CLADOTHRIX 
AND   LEPTOTIIRIX. 

Cultures    of    streptothrix,  differing    from    the  streptothrix 

,.  1  ,  ^  L    •       -\     e  i-\        -\  Infections. 

actmomyces,  have  been  obtained  irom  the  lungs 
in  a  number  of  instances  and  in  various  countries. 
They  have  been  found  in  such  lesions  as  broncho- 
pneumonia, or  more  extensive  consolidation  of  the 
lungs,  and  in  cases  of  empyema.  In  other  instances 
organisms  which  have  been  classed,  some  as  strep- 
tothrix, others  as  cladothrix,  have  been  cultivated 
from  processes  which  resembled  actinomycosis. 

Nocard  considers  a  streptothrix  as  the  cause  of 
farcin  du  tceuf  (farcy  of  cattle),  a  disease  encoun- 
tered especially  in  the  countries  of  southern  Eu- 
rope, and  similar  organisms  have  been  cultivated 
from  suppurating  or  granulomatous  foci  in  other 
animals. 

Leptotlirix  huccalis,  a  thread-like  organism 
which  does  not  form  branches  and,  hence,  is  not  an 
actinomyces  nor  a  streptothrix,  is  frequently  found 
as  a  saprophytic  organism  in  the  mouth  cavity,  and 
a  similar  fungus,  Leptothrix  vaginalis,  has  been 
encountered  in  the  vagina.  Although  organisms 
of  this  type  are  relatively  harmless,  they  have  occa- 
sionally been  found  in  diseased  conditions  of  the 
tonsils  and  pharynx. 

VIII.   OIDIOMYCOSIS. 

In  1894  Gilchrist  described  a  skin  disease,  which 
has  since  been  known  as  blastomycetic  dermatitis, 
or  blastomycosis  or  oidiomycosis  of  the  skin.  From 
a  second  case  he  cultivated  a  fundus  which  at  first 


464  INFECTION    AND    IMMUNITY. 

"Biastomv-  lie  WHS  inclined  to  consider  as  an  oidiuni,  but  later 

cetic"  Der-  n     i         i  i       ,  -,•  i      i    j  • 

matitis.  calletl  a  blastomyces.  femce  that  tnne  many  simi- 
lar cases,  especially  in  Chicago  and  the  adjacent 
territory,  have  been  discovered  and  reported  by 
Wells.  Hektoen,  Hessler,  Hyde  and  Montgomery, 
Ricketts  and  others.  In  many  instances  the  spe- 
cific fungi  have  been  cultivated. 

Systemic  Further  investigations  by  Eixford  and  Gilchrist, 
Busse,  Ophiils  and  Moffit,  Hyde  and  Montgomery 
and  others  have  brought  to  light  the  existence  of 
systemic  infections  by  fungi  which  resemble 
closely  those  found  in  blastomycetic  dermatitis, 
and,  in  fact,  cases  in  which  the  infection  primar- 
ily was  limited  to  the  skin  have  gone  on  to  general- 
ized infection.  The  Saccharomycosis  hominis  of 
Busse  and  Curtis,  blastomycetic  dermatitis,  gen- 
eralized blastomycosis,  and  about  a  dozen  cases  in 
California,  which  at  one  time  were  considered  to 
be  of  protozoon  etiology  (Eixford  and  Gilchrist), 
are  closely  related  or  identical  processes  which  have 
as  their  cause  a  group  of  fungi,  the  individual 
strains  of  which  may  show  considerable  differences. 

Nature  of  In  thoso  cases  usually  described  as  blastomycetic 
dermatitis  or  systematic  blastomycosis,  the  fungus 
proliferates  in  the  tissues  by  budding,  and 
is  found  chiefly  in  the  intraepithelial  and 
subcutaneous  abscesses,  and  in  the  granula- 
tion tissue  and  nodules  of  internal  organs. 
Its  appearance  in  culture  media  and  its  bio- 
logic properties  are  subject  to  considerable 
variations,  at  one  time  growing  as  a  mold,  at  an- 
other time  more  like  the  typical  oidium,  and  again 
resembling  some  form  of  yeast.  Eicketts  considers 
that  the  genus  oidium  is  sufficiently  broad  to  in- 
clude all  the  types  which  have  been  described,  and 


Fungi. 


OIDIOMYCOmH. 


465 


that  blaslomycGs  is  too  narrow.  The  organisms 
which  have  been  cultivated  from  tlie  cases  in  Cali- 
fornia grow  as  molds,  and  they  differ  from  those 
described  by  Gilchrist,  Hektoen,  Eicketts  and  oth- 
ers in  that  they  form  endospores  and  apparently  do 
not  bud  in  the  tissues  of  the  host  (Ophiils,  Wol- 
bach).  Ophiils  calls  this  parasite  Oiclium  cocci- 
dioides,  agreeing  with  Eicketts  as  to  the  generic 
character  of  the  group. 

The  skin  infection  usually  appears  as  a  coarse  Histology. 
warty  and  ulcerative  lesion,  in  which  the  large 
papillas  and  cutaneous  areola  are  beset  with  mi- 
nute abscesses;  the  process  extends  gradually  and 
eventually  may  involve  large  areas.  Histologically, 
the  tissue  shows  an  enormous  epithelial  hyper- 
plasia with  intraepithelial  abscesses,  and  a  richly 
cellular,  granulomatous  condition  of  the  subepithe- 
lial tissue,  in  which  giant  cells  and  small  abscesses 
are  found.  When  the  disease  is  systemic,  various 
internal  organs,  especially  the  lungs,  spleen  and 
kidneys,  are  the  seats  of  abscesses  and  nodules 
which  contain  the  parasites  in  immense  numbers. 
The  lungs  show  lobular  or  more  extensive  consoli- 
dation. 

The  skin  infection  occasionally  follows  slight  infection 
traumatism,  while  in  other  instances  no  predispos- 
ing condition  is  known  by  the  patient.  The  occur- 
rence of  cutaneous  lesions  in  crops  has  been  noted, 
and  suggests  that  in  some  instances  they  may  orig- 
inate as  embolic  foci .  from  a  pulmonary  lesion 
which  later  heals  or  becomes  latent.  In  the  sys- 
temic infection  the  primary  lesion  appears  to  be 
in  the  lungs  in  most  cases,  from  which  the  blood 
and  other  organs,  including  the  skin,  may  be  in- 
vaded.    Pulmonary    oidiomycosis    simulates    pul- 


Atria. 


Systemic 
Infection. 


466  IXFECTl<i\      \\l>    I  \l  Ml   MTV. 

monary  tuberculosis.  In  extensive  involvnnont  of 
the  lungs  the  organisms  may  bo  domonstrated  in 
the  sputum.  At  pi'osent  nothing  is  known  concern- 
ing immunity  to  these  infections. 

TJtriisli. 

Ophiils  very  properly  suggests  that  thrusli 
should  be  considered  as  one  form  of  oidiomycosis. 
Thrush  is  of  particular  interest  because  of  the  early 
date  at  which  its  parasitic  nature  was  recognized. 
Langenbeck  and  Berg,  in  1839  and  1841,  are  cited 
as  the  discoverers  of  the  fungus,  and  they  repro- 
duced the  disease  by  inoculations  with  fragments 
of  the  membrane.  The  parasite  was  studied  a  little 
later  by  Gruby,  Eobin  and  others,  and  the  latter 
gave  it  the  name  of  Oidium  albicans.  Grawitz  ob- 
tained it  in  pure  culture  in  1877  and  demonstrated 
its  pathogenicity  for  dogs  and  rabbits. 

Cultures  of  the  organism  show  differences  in 
size,  morphology,  chemical  activities  and  methods 
of  proliferation,  although  the  variations  are  hardly 
so  wide  as  those  found  among  .the  fungi  cultivated 
from  cases  of  "blastomycosis." 

Although  thrush  usually  is  considered  a  rather 
harmless  affection,  Virchow  long  ago  showed  that 
its  filaments  may  penetrate  the  submucous  tissues 
and  even  the  lumens  of  blood  vessels.  In  rare  in- 
stances systemic  infection,  with  abscesses  in  the 
brain,  kidney  and  spleen  or  with  nodules  in  the 
lungs,  has  been  noted;  in  these  cases  the  condi- 
tions resemble  those  found  in  systemic  "l^lastomy- 
cosis." 

The  healthy  person  has  little  or  no  susceptibility 
to  thrush,  although  a  few  eases  of  infection  have 
been  noted  in  individuals  wlio  were  otherwise  nor- 


OIDIOMYCOHIH.  467 

mal.  Customarily  it  attacks  only  those  wlio  are 
in  a  low  state  of  vitality,  as  poorly  nourished  chil- 
dren or  those  in  advanced  age,  or  those  whose  re- 
sistance is  much  lowered  by  some  other  disease  (ty- 
phoid, diabetes,  etc.). 

Phagocytosis  of  yeast  and  oidium-like  cells  takes  Phagocytosis 
place  when  they  are  placed  in  the  abdominal  cav-  *"''  '"""""'*v. 
ity  of  experiment  animals  (guinea-pigs).  A  num- 
ber of  leucocytes  may  fuse  to  form  a  plasmodial 
mass  around  one  or  more  of  the  parasitic  cells. 
Eoger  and  Noisette  caused  an  increase  in  the  re- 
sistance of  rabbits  to  thrush  infection  by  the  intra- 
venous injection  of  small  doses  of  the  parasite.  Ac- 
cording to  Koisette,  an  immune  serum  agglutinates 
only  the  strain  used  in  the  immunization. 

_  Infections  of  other  animals  (horses,  cattle)  by 
oidium-like  organisms,  the  trichophyton  and  other 
fungi  which  cause  superficial  diseases  in  the  skin 
of  man,  and  other  fungi  (aspergillus,  mucor), 
which  occasionally  are  pathogenic  for  man,  will  not 
be  discussed. 


GEOUP  V. 

PllOTOZOOX    INFECTIONS. 
I.    MALAEIA. 

Etiology.  The  etiolog}'  of  malaria,  which  for  long  was 
supposed  to  be  associated  with  impure  and  swampy 
atmospheres  (malaria  is  from  mal'  aria,  Italian 
meaning  bad  air),  remained  unknown  until  1880, 
when  Laveran  discovered  ameboid,  half-moon 
shaped  and  flagellated  forms  of  a  parasite  in  the 
blood  of  the  patients.  In  following  years  Golgi, 
Grassi,  Marcliiafava  and  Celli  and  many  others 
took  prominent  parts  in  working  out  the  different 
forms  of  parasites,  their  sexual  characters  and  their 
relation  to  the  different  types  of  malaria. 

Ross  and  The  Conception  that  mosquitoes  may  be  influen- 
tial  m  transmittmg  malaria  is  a  very  old  one  and 
its  origin  is  unknown.  In  1894  Manson  suggested 
that  the  malarial  organism  may  utilize  the  mos- 
quito as  an  intermediate  host  where,  after  under- 
going further  development,  it  again  becomes  in- 
fectious for  man.  He  was  inclined  to  think  that 
the  flagella  are  reproductive  forms,  which  are 
essential  for  an  extra  corpus  life  of  the  parasite. 
The  proof  of  this  came  from  MacCallum  in  1897, 
who  showed  that  the  flagellated  forms  are  really 
spermatozoites,  the  function  of  which  is  to  im- 
pregnate female  cells  of  the  parasite.  This  was 
observed  first  in  relation  to  halteridium,  one  of 
the  organisms  of  avian  malaria,  and  later  in  rela- 
tion to  the  parasites  of  human  malaria. 

In  the  same  year  Eoss  found  the  pigmented, 
half-moon    shaped    parasites    of    ffistivo-autumnal 


MALARIA. 


469 


fever  in  the  stomach  of  the  anopheles  mosquito. 
Through  the  work  of  Eoss  and  others  it  is  now 
established  that  the  malarial  parasite  undergoes 
further  development;,  a  sexual  cycle,  in  anopheles, 
and  that  man  is  inoculated  only  by  the  bites  of 
such  infected  insects.  From  the  standpoint  of 
the  zoologist,  man  is  an  intermediate  host  for  the 
parasite,  since  the  latter  undergoes  its  higher  de- 
velopment only  after  it  reaches  the  mosquito. 

The  malarial  parasites  of  man  belong  to  the 
class  of  Sporozoa;  order,  Coccidiomorpha ;  family, 
Hemosporidia ;  genus,  Plasmodium.  The  follow- 
ing are  the  names  given  to  the  three  species :  1. 
Plasmodium  prgecox  (parasite  of  gestivo-autumnal 
fever)  ;  2.  Plaismodium  vivax  (of  tertian  fever)  ; 
3.  Plasmodium  malarias  (of  quartan  fever) . 

When  the  blood  of  one  suffering  from  tertian 
fever  is  examined  at  the  end  of  the  febrile  parox- 
ysm, or  at  the  beginning  of  the  afebrile  stage,  the 
parasites  are  found  within  the  erythrocytes  as  pale, 
rather  clear  bodies,  about  one-fifth  the  diameter  of 
the  corpuscle,  and  in  fresh  specimens  showing  an 
active  ameboid  movement.  They  are  very  difficult 
to  recognize  in  unstained  specimens.  They  increase 
in  size  gradually,  and  after  eighteen  hours,  when 
they  begin  to  acquire  pigment,  they  are  recognized 
more  easily.  After  twenty-four  hours  the  pig- 
ment has  increased  markedly  and  the  erythrocytes 
are  swollen  and  pale.  In  stained  preparations  the 
periphery  of  the  parasite  stains  more  deeply  than 
the  center  and  gives  it  a  pronounced  ring  form. 
At  the  end  of  thirty-six  hours  they  have  increased 
noticeably  in  size  and  their  ameboid  motion  is 
less.  Shortly  before  the  next  attack — i.  e.,  forty- 
six  to  forty-eight  hours  after  the  preceding  one — 


Species  of 
Plasmodium. 


Tertian 
Fever. 


470 


ISFECTION   AXJ)    IMMIMTY. 


Sexual 
Cells. 


Segmentation  I  lie  pigiucut  asscmblcs  iiilo  oiic  01"  two  gvoups  in 
^ceUs.  tlie  center  of  the  parasite  and  clear  hyaline  points 
begin  to  appear.  These  are  the  young  endocellular 
parasites  which  are  formed  by  division  of  the  nu- 
cleus of  the  mother  cell.  They  gradually  increase 
in  size  and  number,  and  as  the  red  corpuscles  disin- 
tegrate they  are  discharged,  from  fifteen  to  twenty- 
five  in  number,  as  young  parasites.  This  completes 
the  cycle,  an  asexual  cycle,  which  has  lasted  forty- 
eight  hours,  and  the  young  forms  then  begin  a 
new  cycle  after  penetrating  other  red  corpuscles. 
The  mother  cell  is  called  the  sporocyte  and  its 
ofl'spring  are  merozoites,  and  the  process  of  divi- 
sion schizogony. 

In  addition  to  the  asexual  cell  just  described, 
two  sexual  cells,  a  male  and  a  female,  grow  to 
adult  size  in  the  erythrocytes,  acquire  pigment  and 
eventually  become  free.  They  differ  from  the 
asexual  cell  in  that  the  pigment  continues  to  be 
uniformly  distributed,  and  neither  gives  rise  to 
young  parasites  by  division.  The  male  cell  (micro- 
gametocyte,  8-9  microns)  has  a  clear  protoplasm 
and  is  smaller  than  the  female  (macrogamete, 
10-14  microns)  ;  the  female  has  a  granular  proto- 
plasm. There  are  many  more  male  than  female 
cells.  They  undergo  no  further  development  in 
the  body  of  man,  and  in  order  that  the  sexual  pro- 
cess be  completed  the  two  cells  must  first  gain  en- 
trance into  the  stomach  of  the  female  anopheles 
mosquito. 

Impregnation.  A  further  step  in  the  sexual  process  may  be  seen 
in  drop  preparations  of  the  blood,  although  this 
step  does  not  occur  in  the  human  body.  Ten  to 
twenty  minutes  after  such  a  preparation  has  been 
made  the  male  cells,  after  a  period  of  agitation, 


MALARIA.  'ill 

discharge  from  four  to  eight  long,  thin  flagella 
(microgametes  or  spermatozoa),  which  thrash 
about  violently  and  eventually  come  in  contact  vi'ith 
a  female  cell,  which  they  enter  and  become  un- 
recognizable. 

This  same  process  is  instituted  and  completed  Life  in  the 
(sporogony)  in  the  stomach  of  the  mosquito,  the 
penetration  of  the  female  cell  by  the  spermatozoon 
resulting  in  the  impregnation  of  the  former.  Pol- 
lowing  impregTiation,  the  female  cell  gradually 
assumes  a  Avorm-like  or  sickle  shape  (ookinet), 
penetrates  the  wall  of  the  stomach  and  becomes 
encapsulated  (oocyst).  Forty-eight  hours  after 
the  mosquito  has  sucked  malarial  blood  all  the 
female  cells  have  reached  this  stage  and  no  more 
free  parasites  are  found  in  the  stomach. 

About  five  days  after  the  blood  was  taken  the  Formation  of 

,    -,  .  •',..  1J.-.-  n     Sporozoites. 

oocyst  has  increased  m  size  about  six  times  and 
has  formed  within  itself  a  number  of  small 
spheres,  which  are  called  daughter  cysts  or  sporo- 
blasts.  The  latter  soon  acquire  a  finely  striated  ap- 
pearance, which  is  due  to  the  formation  of  hun- 
dreds of  "germinal  rods"  or  sickle-like  bodies 
(sporozoites).  The  latter  are  nothing  less  than 
young  malarial  parasites,  which  are  thrown  into 
the  body  cavity  by  the  rupture  of  the  oocyst,  and 
are  carried  to  the  salivary  glands  of  the  mosquito 
by  the  lym]3hatic  circulation.  If  the  mosquito  has 
been  kept  at  a  temperature  of  24°  to  30°  C.  these 
sickle  forms  first  appear  in  the  salivary  gland  after 
eight  to  ten  days.  Such  are  the  cells  which  are 
inoculated  into  man  by  the  bite  of  the  mosquito. 
The  changes  which  they  undergo  before  they  ap- 
pear as  clear  oval  bodies  in  the  erythrocytes  are 
unknown. 


472 


IXFECTIOy    AXD   IMMLXITY 


Parasite  of 

Quartan 

Fever. 


Parasite  of 

Aestivo-Au- 

tumnal  Tever. 


"Half-moon" 
Cells. 


The  asexual  cycle  of  the  quartan  parasite  is 
identical  Avith  that  of  the  tertian,  with  the  excep- 
tion that  seventy-two  hours  are  required  for  its 
completion.  It  contains  more  pigment,  and  wlien 
division  takes  place  eight,  or  at  most  fourteen, 
young  parasites  are  formed,  in  contrast  to  the 
lifteen  to  twenty-five  of  the  tertian  parasites.  The 
er3^throcytes  do  not  become  large  and  pale  (Ruge). 
The  sexual  cells  practically  are  indistinguishable 
from  those  of  the  tertian  parasite,  although  they 
are,  on  the  whole,  slightly  smaller.  The  sexual 
cycle  also  is  completed  only  in  the  body  of  the 
female  anopheles  mosquito,  and  is  identical  with 
that  of  the  tertian  parasite. 

The  parasite  of  aestivo-autumnal  fever  is  one- 
half  to  two-thirds  the  size  of  the  tertian  parasite, 
a  difference  which  is  constant  in  the  various  stages 
of  development  of  the  asexual  cell.  It  divides 
eventually  into  eight  to  twenty-five  young  para- 
sites, the  cycle  occupying  from  twenty-four  to 
forty-eight  hours. 

Here,  as  in  quartan  fever,  the  erythrocytes  do 
not  become  swollen  and  pale,  but  even  appear 
darker  in  color,  because  of  some  shrinking  (Euge). 
The  sexual  cells  in  asstivo-autumnal  fever  are 
characteristic.  Whereas  they  at  first  do  not  differ 
in  shape  from  the  asexual  cells,  as  they  grow  older 
they  gradually  assume  the  shape  of  a  half  moon  in 
one  edge  of  the  erythrocyte,  reaching  a  length 
equal  to  one  and  one-half  diameters  of  the  red  cell. 
At  this  time  a  fine  line  drawn  across  the  concavity 
of  the  parasite  represents  the  margin  of  the  ery- 
throcyte. This  form  is  only  temporary,  however; 
they  subsequently  assume  first  a  vspindle  and  then 
a  spherical  form.     As  in  the  other  parasites,  the 


MALARIA. 


473 


male  cell  is  rather  clear  and  the  female  granular. 
When  mounted  in  a  hanging  drop  the  male  cell 
liberates  flagella,  which  penetrate  the  female  cell. 
This  does  not  occur  in  the  human  body.  In  this 
respect,  and  also  in  the  completion  of  the  sexual 
cycle  in  the  body  of  the  mosquito,  they  resemble  the 
other  two  parasites. 

The  parasites  of  tertian  and  quartan  fevers  un- 
dergo division  while  they  are  in  the  circulating 
blood,  and  when  peripheral  blood  is  examined  at  the 
end  of  the  afebrile  stage  the  young  cells  may  be 
found  extracellular.  This  is  not  the  case,  how- 
ever, in  the  gestivo-autumnal  fever.  In  this  in- 
stance, for  unknown  reasons,  the  adult  cells  with- 
draw to  the  internal  organs,  especially  the  spleen, 
bone-marrow  and  brain,  where  division  takes  place 
in  the  minute  vessels.  Hence  if  the  peripheral 
blood  is  examined  preceding  and  during  the  febrile 
stage  few  or  no  dividing  cells  or  young  parasites 
are  seen. 

Following  inoculation  by  an  infected  mosquito, 
ten  to  twelve  days  are  required  for  the  onset  of  a 
paroxysm.  In  rare  instances  the  incubation  period 
may  be  as  short  as  five  to  six  days.  This  probably 
depends  to  some  extent  on  the  number  of  organisms 
inoculated.  Malarial  infection  of  the  mosquito 
is-  not  transmitted  to  the  offspring  the  latter,* 
hence  the  bites  of  young  mosquitos  do  not  convey 
the  disease  unless  they  also  have  sucked  malarial 
blood.  The  conditions  are  different  in  relation 
to  Texas  fever,  in  which  the  infection  is  trans- 
mitted by  the  female  tick  to  her  young. 

The    ffistivo-autumnal    parasite    apparently    is   virulence 
more  virulent  than  the  tertian  or  quartan.     Not 


Incubation 
Period. 


*  This  is  questioned  by  Schaudinn. 


474 


IXFECTIOy   A\n    IMMUNITY. 


Relation  of 

S>niptonis  to 

the  Bioloqv  of 

the  Parasites. 


all  cases  of  tertian  or  quartan  fever  are  equally 
severe,  and  these  variations  may  depend  on  diU'cr- 
ences  both  in  virulence  and  in  the  resistance  of  in- 
dividuals. "When  all  the  parasites  divide  within  a 
period  of  two  to  four  hours,  the  paroxysm  is  more 
intense  but  shorter  than  when  division  extends 
over  six  to  eight  hours  (Ruge  in  relation  to  ter- 
tian fever).  Some  of  the  severer  symptoms  are 
due  to  the  localization  of  the  jiarasitcs  (brain  and 
intestines),  rather  than  to  special  toxicity. 

The  melanemia  of  malarial  fevers  is  due  to  the 
fact  that  the  parasites  absorb  the  hemoglobin  from 
the  erythrocytes,  transform  it  into  melanin  by 
their  metabolic  activities  and  liberate  the  melanin 
at  the  time  of  cell  division.  The  anemia  results 
from  destruction  of  the  erythrocytes. 

The  cause  of  the  fever  and  its  periodic  recur- 
rence is  more  difficult  to  explain.  As  stated  above, 
the  fever  begins  in  both  tertian  and  quartan  fevers 
at  the  time  division  forms  of  the  parasites  are  en- 
countered in  the  perif)heral  blood.  Although  all 
the  parasites  do  not  divide  simultaneously,  the 
process  is  complete  within  a  period  of  four  to 
eight  hours  and  the  parox}'sm  begins  early  in  this 
Fever  and  period.  It  is  quitc  natural,  then,  to  infer  that  by 
the  division  of  the  parasite  and  the  escape  of  the 
young  cells  from  the  erythrocytes,  toxic  substances 
are  thrown  into  the  circulation,  and  that  the  febrile 
reaction  is  due  to  the  action  of  these  toxins. 
Methylene  blue  has  the  power  of  preventing  seg- 
mentation of  the  parasites  (Ehrlich),  and  it  has 
been  shown  that  the  paroxysm  of  fever  may  be 
averted  by  administering  methylene  blue  at  the 
proper  time.  This  corroborates  the  view  that  the 
segmentation  of  the  parasites  causes  fever  in  some 


Schizogony. 


MALARIA. 


475 


way.  The  paroxysm  would  seem  to  represent  the 
time  required  for  the  exhaustion  of  the  toxins  set 
free  at  the  time  of  the  cell  division.* 

On  the  basis  of  the  conditions  just  cited,  the 
brief  duration,  sharp  limitation  and  regular  re- 
currence of  the  paroxysms  in  tertian  and  quartan 
fevers  become  intelligible.  In  a  similar  manner 
the  longer  paroxysms  and  shorter  intermissions 
which  characterize  the  typical  ffistivo-autumnal  in- 
fection (i.  e.,  in  first  attacks)  are  related  to  the 
habits  of  division  of  the  corresponding  parasite. 
All  the  cells  do  not  divide  within  a  relatively  short 
period,  as  in  tertian  and  quartan  fevers,  but  the 
process  of  division  rather  stretches  out  over  from 
twenty-four  to  forty-eight  hours.  This  accounts 
for  the  longer  duration  of  the  paroxysm.  When 
the  last  cells  of  one  generation  are  dividing,  per- 
haps after  the  fever  has  gone  down,  the  first  cells 
of  the  succeeding  generation  are  well  on  toward 
maturity  and  their  division  within  a  short  time 
inaugurates  a  new  paroxysm;  the  brief  intermis- 
sion would  seem  to  be  explained  by  this  condition. 
As  the  disease  lasts  longer,  or  as  relapses  develop, 
the  periods  of  division  of  the  parasite  are  less 
sharply  limited  and  a  course  with  an  irregularly 
continuous  (?)  fever  may  be  established. 

Quotidian  malarial  fever  is  caused  either  by 
a  double  infection  with  tertian  parasites  or  a 
triple  infection  with  quartan  parasites.  In  either 
instance  a  generation  of  parasites  matures  and 
divides  ever}'  twenty-four  hours.     The   cause  of 


Duration  of 
Paroxysms. 


Quotidian 
Fever. 


*  Ivosenan,  Parker,  Francis  and  Beyer  produced  a  typical 
paroxysm  in  a  healthy  person  by  injecting  filtered  serum 
taken  from  a  tertian  patient  during  the  chill.  This  was 
intoxication,   not  infection. 


476  IXFECTIOX    AXD    IMMIXITY. 

the  double  or  triple  infection  is  not  known  definite- 
ly. In  some  instances  it  is  possible  that  successive 
inoculations  by  different  mosquitoes  has  occurred. 
On  the  other  hand  a  fever  which  is  primarily  ter- 
tian or  quartan  may  gradually  change  into  the 
quotidian  variet}',  and  in  this  condition  it  is  pos- 
sible that  the  organisms  may  gradually  separate 
themselves  into  two  or  three  distinct  generations, 
which  reach  maturity  on  successive  days. 
Mixed       In  other   instances   mixed   infection   witli   two 

Infections.    ,  .     ,         „  .  .  ,         t        mi  •      •  n 

kinds  of  parasites  is  encountered.  This  is  usually 
ffistivo-autumnal  fever  combined  either  with  ter- 
tian or  with  quartan.  Either  the  asstivo-aiitumnal 
may  be  primary  on  the  one  hand  or  the  tertian  or 
quartan  on  the  other.  The  clinical  course  is  com- 
plicated correspondingly.  It  is  doubtful  if  tertian 
infection  is  ever  mixed  with  quartan.  Eugc  speaks 
of  experiments  by  Dr.  Mattel  which  indicate  that 
a  mixed  infection  does  not  continue  indefinitely 
as  such.  A  patient  suffering  from  quartan  fever 
was  inoculated  with  sestivo-autumnal  blood;  in 
time  all  the  quartan  parasites  disappeared,  leav- 
ing only  the  gestivo-autumnal. 

In  malarial  cachexia  there  is  not  only  an  in- 
sufficiency of  the  blood-forming  organs,  but  other 
parenchymatous  organs  have  suffered  as  a  result 
of  prolonged  intoxication.  The  blood-forming  or- 
gans can  not  keep  pace  with  the  destruction  of  the 
erythrocytes.     . 

Trigeminal  and  supraorbital  neuralgias  and 
periodic  headaches  occur  sometimes  as  accompani- 
ments of  malarial  infection,  even  when  there  is 
little  or  no  fever,  and  no  parasites  may  be  dis- 
coverable in  the  blood.  That  they  are  malarial  in 
origin  is  concluded  from  the  fact  that  they  subside 
under  quinin  treatment. 


MALARIA. 


477 


In    some    forms,  and    particularly    m    a3stivo-   Cerebral 

,  1    J.  11  ,  /  X      and  Intesti- 

autumnal  lever,  cerebral  symptoms  (e.  g.,  coma)  nai  Symptoms. 
are  marked  by  accumulations  of  the  parasites  in 
the  small  vessels  of  the  brain;  tbc  vessels  may  be 
completely  occluded.  The  conditions  arc  similar 
in  the  small  vessels  of  the  intestines  in  malarial 
diarrheas. 

The    so-called   "black-water    fever,"   or  hemo-  "Black-water 

'  Fever." 

globinuric  fever,  is  not  a  special  form  of  malaria, 
but  a  complication  which,  it  is  thought,  is  pre- 
cipitated by  insufficient  or  improper  administra- 
tion of  quinin  (Koch  and  others).  It  is  most  fre- 
quent in  the  tropics,  hence  in  sestivo-autumnal 
fever,  but  may  occur  in  the  tertian  and  quartan 
types.  Various  observers  have  found  that  in  all 
the  way  from  56  per  cent,  to  97  per  cent,  of  the 
cases  quinin  precipitated  attacks.  Stephens  and 
Christopher  were  not  able  to  exclude  quinin  as  a 
factor  in  any  of  the  cases- they  encountered.  The 
essential  process  is  a  massive  destruction  of  the 
erythrocytes  which  is  entirely  out  of  proportion  to 
the  number  of  cells  occupied  by  parasites:  few  or 
no  parasites  may  be  present.  The  amount  of 
hemoglobin  thus  liberated  is  so  great  that  it  is  ex- 
creted largely  by  the  kidneys;  anuria  may  result 
from  occlusion  of  the  tubules  by  pigment.  How 
the  quinin,  or  the  quinin  plus  parasites,  produce 
this  extensive  hemolysis  is  entirely  obscure;  the 
effect  is  that  of  an  intense  intoxication,  in  which 
the  erythrocytes  suffer  primarily  and  chiefl3^ 

The  essential  epidemiologic  features  of  malaria  Epidemiology. 
are  the  following :  It  prevails  especially  in  tropical 
and  subtropical  zones  and  less  in  temperate  zones. 
It  is  most  abundant  in  low,  swampy  regions,  and 
in  other  places  which  afford  quiet  streams,  ponds 


478 


IXFECriOX    AM)    nnil  MTY. 


or  other  standing  Avater.  Malaria  is  not  directly 
contagious.  In  order  to  hocoine  infected  it  is 
necessary,  customarily,  for  one  to  enter  or  be  in 
close  proximity  to  a  "malarial  district."  That 
the  virus  is  not  carried  far  from  an  infected  dis- 
trict is  shown  by  the  exemption  of  the  crews  of 
vessels  which  lie  within  two  or  three  miles  of  such 
a  district.  Infection  has  long  been  supposed  to 
take  place  chiefly  by  night.  The  disease  may  be 
introduced  into  new  regions  (of  suitable  climate) 
by  the  importation  of  malarial  subjects.  These 
and  many  other  phenomena  of  malaria  which  were 
once  very  obscure  have  been  cleared  up  by  the 
mosquito  theory. 
Anopheles.  There  arc  many  species  of  anopheles  and  they 
are  distributed  throughout  the  world  in  warm  and 
moderate  climates.  Anopheles  inacuUpennis  is 
the  most  numerous  species,  and  for  it,  as  well  as 
for  Anopheles  punctipennis,  Howard  has  found 
several  natural  breeding  places  in  this  country. 
It  is  probable  that  many,  but  not  all,  species  of 
anopheles  may  transmit  malaria.  The  female 
only  is  a  blood-sucker,  the  male  living  on  vegetable 
material  exclusively.  After  the  female  has  ob- 
tained blood  from  man  or  another  mammal  it  flies 
to  a  suitable  pond  or  other  collection  of  w^ater, 
where  it  deposits  its  eggs. 
Development  "The  adult  mosquito  lays  its  eggs  on  the  surface 
of  the  water.  The  eggs  float  on  the  water  for 
some  days  (tw^o  to  four),  after  wliieh  tlicy  hatch 
and  permit  the  escape  of  the  larva. 

"The  larva  is  a  free-swimming,  worm-like  ani- 
mal, which  eats  greedily  and  grows  rapidly,  cast- 
ing its  skin  several  times  in  the  process,  till  it 
reaches  its  full  development.    At  this  stage  it  sud- 


MALARIA.  479 

denly  changes  its  form;  casting  its  skin,  the  worm- 
like larva  assumes  a  comma  shape  and  so  becomes 
the  pupa  or  nymj)ha. 

"During  the  pupal  period  the  insect  ceases  to 
eat;  profound  anatomical  changes  take  place  with- 
in the  pupal  skin,  whereby  the  masticatory  mouth - 
parts  of  the  larva  are  converted  into  the  suctorial 
apparatus  of  the  adult  insect  or  imago.  After  a 
certain  number  of  days  the  pupa  case  ruptures  and 
the  adult  insect  is  liberated,  furnished  with  wings 
and  legs  adapted  for  a  life  in  the  air."  (James 
and  Liston.) 

In  one  instance  Howard  found  the  life  cycle  of 
Anopheles  macuUpennis  to  be:  "Egg  stage,  three 
days;  larval  stage,  sixteen  days;  pupal  stage,  five 
days,  making  a  total  period  in  the  early  stages  of 
twenty-four  days."  The  rapidity  with  which  this 
process  takes  place  depends  largely  on  the  tem- 
perature; it  is  more  rapid  in  the  hot  weather  of 
July  and  August  than  in  the  cold  days  of  May. 
Anopheles  usually  does  not  lay  its  eggs  in  tin  cans 
or  barrels  of  water,  but  preferably  in  more  open 
or  cleaner  water.  Excavations  which  have  become 
filled  with  water  are  favorable  places,  as  are  also 
collections  of  water  from  springs'. 

The  anopheles  leads  an  adult  life  for  many 
months  and  may  even  hibernate  under  suitable 
conditions  either  in  the  adult  or  larval  form.  It 
is  generally  stated  that  the  insects  do  not  fly  more 
than  half  a  mile  from  their  breeding  and  feeding- 
grounds.  Their  dispersal  certainly  extends  beyond 
these  limits,  however.  James  and  Liston  enumer- 
ate the  following  methods  of  dispersal :  1.  By 
direct  flight  over  considerable  distances.  2.  By 
the  eggs  and  larvae  being  carried  in  streams  and 


Migration  of 
Anopheles. 


480 


IXFECTIOX   AXD   IMMUNITY. 


Prophylaxis. 


General 
Measures. 


canals.  3.  By  a  multiplication  of  successive  short 
flights  by  adults.    4.  In  conveyances. 

Anopheles  avoicls  high  winds  and  rains,  seeks 
shelter  on  excessively  hot  days  and  feeds  and  bites 
chiefly  or  only  after  sunset  and  before  sunrise. 
The  latter  habit  confirms  the  old  belief  that  ma- 
larial infection  occurs  chiefly  at  night. 

For  further  details  as  to  the  morphology  and 
habits  of  the  insect  in  its  different  stages,  and  for 
differentiation  of  the  different  genera  and  spe- 
cies, one  should  consult  a  textbook  of  entomology, 
or,  for  example,  the  book  on  "Mosquitos,"  by  How- 
ard (McClure,  Phillips  &  Co.,  New  York). 

Individual  prophylaxis  may  be  accomplished  and 
maintained  by  taking  small  daily  doses  of  quinin, 
or  larger  doses  (1  gram)  every  few  days.  One  who 
has  had  malaria  may  likewise  prevent  recurrence 
by  suitable  quinin  treatment.  Quinin  has  the 
power  of  preventing  division  of  the  parasites,  and, 
therefore,  the  power  of  preventing  the  paroxysms. 
"R.  Koch's  procedure  consists  in  this,  that  one 
takes  a  gram  of  quinin  every  tenth  and  eleventh 
day,  and  if  fever  still  develops,  every  ninth  and 
tenth  day."     (Euge.) 

Other  points  in  individual  prophylaxis  are,  first, 
the  application  of  ethereal  oils  (clove  oil,  oil  of 
pennyroj^al)  to  the  exposed  skin,  and,  second,  the 
use  of  mosquito  netting. 

The  important  practices  for  general  prophylaxis 
are  the  following:  1.  The  draining  of  swampy 
places  and  of  jdooIs  of  water  W'here  anopheles  may 
deposit  its  eggs.  This  in  many  instances  manifest- 
ly can  not  be  accomplished.  2.  Covering  pools  of 
water  with  petroleum.  This  is  to  a  degree  success- 
ful.    Every  square  meter  requires  i/o  liter  of  pe- 


MALARIA.  481 

troleiim  (Kerschbatimer),  and  the  oil  must  be 
added  fresh  every  seven  or  eight  days.  The  layer 
of  oil  excludes  the  air  from  the  larval  mosquitoes 
and  they  drown.  If  fresh  oil  is  not  added  occa- 
sionally new  eggs  may  hatch.  3.  Koch's  method  of 
extermination  of  malaria.  This  consists  of  the 
searching  out  of  all  cases  of  malaria  and  the  de- 
struction of  the  parasites  by  appropriate  quinin 
treatment.  Koch  practiced  this  method  in  an  in- 
fected locality  of  New  Guinea  and  in  a  relatively 
short  time  freed  it  of  malaria.  If  all  the  plasmodia 
in  a  community  are  destroyed  the  disease  can  not 
again  become  endemic  unless  it  is  introduced  from 
without  or  unless  infected  mosquitoes  are  imported. 
Manifestly  this  method  must  be  practiced  on  an  ex- 
tensive scale  in  order  to  render  it  permanently 
successful.  It  seems  to  have  been  demonstrated, 
however,  that  the  number  of  cases  in  any  given 
locality  may  be  materially  decreased  by  pursu- 
ing it. 

So  far  as  is  known,  susceptibility  to  malaria  is  immunity. 
universal.  The  belief  is  very  general  that  one 
attack  of  malaria  not  only  does  not  protect  against 
reinfection,  but  even  predisposes  to  it.  Two  facts, 
however,  show  that  acquired  immunity  (relative 
or  absolute)  is  possible.  First,  in  certain  regions 
of  Africa  where  malaria  is  endemic  the  adult  na- 
tives rarely  suffer  from  the  disease,  and  then  only 
from  light  attacks,  whereas  European  visitors  con- 
tract the  disease  in  severe  form.  The  cause  of  this 
immunity  was  explained  by  Koch.  "Koch  found 
that  the  native  adults  of  malarial  countries  were 
free  from  malaria,  but  that  the  children  suffered 
almost  universally  from  malarial  diseaises.  If 
they  recovered  from  the  original  infection  they 


482  INFECTION  AM)  IMMUNITY. 

became  immunized  in  time  through  continued  new 
attacks  or  relapses,  the  number  of  malarial  chil- 
dren gradually  decreased  with  their  age,  and  in  the 
vicinity  of  the  tenth  year  the  only  evidence,  in 
general,  of  a  previous  infection  was  an  enlarged 
spleen,  and  even  this  disappeared  during  puberty, 
so  that  the  adult  natives  finally  appeared  as 
healthy  and  malaria-immune  persons."  (Ruge.) 
The  objection  raised  by  many  that  such  immunity 
is  not  observed  in  Italy  and  other  civilized  coun- 
tries where  malaria  is  endemic,  is  met  by  the  fact 
that  the  disease  in  these  countries  is  not  permitted 
to  run  an  uninterrupted  course.  Treatment  with 
quinin  is  instituted  and  the  immunizing  process 
is  thereby  broken  off.  Koch  also  established  that 
immunity  against  one  type  of  parasite  is  not  effi- 
cient against  other  types. 

Second,  in  civilized  countries  it  has  often  been 
noted  that  subsequent  attacks  are  of  a  milder  char- 
acter than  the  primary;  the  disease  may  in  time 
"wear  itself  out,"  even  without  quinin  treatment. 
Ruge  gives  as  an  accompaniment  of  this  immuniz- 
ing process  the  occurrence  of  the  sexual  cells  in 
large  numbers,  even  up  to  50  per  cent,  of  the  total 
number  of  parasites  (tertian  fever).  In  such 
cases  large  numbers  of  the  parasites  die  before 
they  reach  maturity,  their  death  being  indicated 
by  shrinking  and  clouding  of  the  cells  and  altera- 
tions in  or  disappearance  of  the  chromatin.  It  is 
somewhat  characteristic  of  quartan  fever,  and  still 
more  so  of  sestivo-autumnal,  that  the  sexual  cells 
are  much  more  numerous  in  recurrences  than  in 
primary  attacks.  One  may  be  able  to  differentiate 
a  relapse  from  the  primary  attack  by  the  number 
of  sexual  cells  encountered  (Ruge). 


TUYPANOSOMIASIS. 


483 


Proteosome. 


N'o thing  in  the  way  of  serum  therapy  has  been 
accomplished,  and  it  is  doubtful  if  any  serum 
could  equal  quinin  in  efficacy. 

MALARIA     OF    BIRDS. 

Wliat  is  considered  as  true  malaria  also  occurs  in  birds. 

One  of  these  diseases  is  caused  by  a  proteosome  {Pro- 
teosoma  Labhe,  Cystosporon  danielewslcy,  Hemameha  re- 
licta).  Sparrows,  hawks,  buzzards,  crows  and  pigeons 
are  aflfected.  Like  the  malarial  parasites  in  man,  the 
parasite  enters  the  erythrocytes  and  has  both  a  sexual 
and  an  asexual  cycle  of  development,  the  latter  taking 
place  in  the  infected  animal,  the  former  in  the  stomach 
-of  the  common  mosquito  (Culex  pipiens) .  Hence  in  its 
development  proteosoma  is  perfectly  analogous  to 
Plasmodium.  The  disease  is  transmissible  from  bird  to 
bird  by  the  inoculation  of  infected  blood. 

Halteridium  is  still  another  hemosporidium  which  in-  'Halteridium. 
-fects  birds.  It  was  in  the  study  of  this  organism  that 
MacCallum  first  saw  the  phenomenon  of  impregnation. 
All  the  cells  seen  in  the  blood  appear  to  be  divisible  into 
male  and  female,  and  although  MacCallum  had  seen  im- 
pregnation in  microscopic  preparations  the  life  cycle  for 
a  long  time  was  obscru-e.  Recently  Schaudinn  has  found 
that  the  sexiial  cycle  is  completed  in  Culex  pipiens.  He 
considers  the  organism  to  be  a  trypanosome.  "I  have 
been  able  to  prove  that  the  halteridium  is  the  sexual 
stage  of  a  trypanosome  which  multiplies  in  the  common 
mosquito — Culex  pipiens — and  after  a  complicated  mi- 
gration through  the  body  of  the  mosquito  is  again  in- 
troduced by  its  bite  into  the  blood  of  the  owl,  where, 
a,fter  a  period  of  sexual  multiplication,  it  is  transformed 
into  the  Avell-known  male  and  female  halteridium." 


II.     TETPANOSOMIASIS. 

Gruby  created  the  genus  Trypanosoma  in  1843^ 
when  he  gave  the  name  of  Trypanosoma  sanguinis 
to  a  flagellate  protozoon  which  he  found  in  the 
ialood  of  frogs.  Since  that  time  similar  organisms 
have  been  found  in  the  bloods  of  many  animals  and 
the  genus  Trypanosoma  has  grown  to  considerable 


Genus 
Trypanosoma. 


484  IXFECTIOX  AM)  IM.yUMTY. 

dimensions.  It  is  not  improbalile.  liowcver,  that 
a  niunber  which  now  bear  indepcmU'iit  names  will 
be  shown  to  be  identical.  This  suggests  itself  par- 
ticularly in  relation  to  trypanosomiasis  in  horses, 
in  which  the  infections  are  loiown  under  four  sep- 
arate names  in  different  countries,  and  the  para- 
sites are  given  separate  specific  names.  The  study 
of  these  infections  is  so  young  and  has  been  prose- 
cuted in  such  widely  separated  countries  that  the 
existing  chaos  is  quite  natural  and  can  be  adjusted 
only  as  time  and  circumstances  permit  of  close 
comparative  study.  Until  such  a  time  the  prevail- 
ing views  as  to  independence  of  species  and  of  in- 
fections must  be  recognized. 
Morphorogy.  Trypanosomas  vary  a  great  deal  in  size  and  mor- 
phology. Eoughly,  they  are  from  one  to  five  mi- 
crons thick  and  fifteen  to  forty-five  microns  long, 
including  the  flagellum.  All  species  possess  active 
eel-like  movements,  some  traveling  rapidly,  others 
slowly.  A  long,  actively-motile  flagellum  projects 
from  the  anterior  end,  and  where  it  joins  the  cell 
body  is  continuous  with  an  "undulating  mem- 
brane," which  extends  along  a  border  of  the  or- 
ganism to  a  point  near  the  centrosome  or  micronu- 
cleus  in  the  posterior  portion  of  the  cell.  The 
centrosome  is  sometimes  spoken  of  as  analagous 
to  the  "eye  spot"  of  some  other  protozoa.  The  un- 
dulating membrane  is  more  or  less  wavy  or  folded 
and  its  breadth  varies.  The  centrosome  presum- 
ably has  a  close  relationship  to  the  undulating 
membrane,  and,  through  the  latter,  with  the  flagel- 
lum. The  nucleus  is  in  the  anterior  portion  of 
the  parasite.  In  relation  to  some  species  a  con- 
tractile vacuole  is  spoken  of.  An  endoplasm  and 
an  ectoplasm  may  be  differentiated. 


TRYPANOSOMIASIS. 


485 


Division  of  trypanosomes  is  nearly  always  longi-  Division 
tudinal,  rarely  transverse.  According  to  Piimmer 
and  Bradford,  conjugation  may  occur,  "followed 
by  an  ameboid  stage  and  division  by  segmenta- 
tion." The  ameboid  stage  at  times  occurred  inde- 
pendently of  conjugation.  (Musgrave  and  Clegg.)* 
In  the  process  of  longitudinal  fission  the  order  of 
division  of  the  different  parts  of  the  cell  is  as  fol- 
lows :  1,  Centrosome ;  3,  flagellum ;  3,  nucleus  and 
protoplasm  (Laveran  and  Mesnil).  After  division 
has  occurred  the  two  cells  may  remain  attached 
at  their  posterior  ends  for  some  time.  By  a  re- 
peated division  of  young  cells,  the  posterior  ends 
remaining  attached,  rosettes  are  said  to  be  formed. 
Others  consider  rosette  formation  as  a  phenomenon 
of  agglutination.    Possibly  both  phenomena  occur. 

Trypanosomas  are  differentiated  on  the  basis  of 
size,  pathogenicity,  motility  and  certain  points  in 
morphology,  as  the  position  and  size  of  the  micro- 
nucleus  or  centrosome,  the  presence  of  a  contractile 
vacuole,  the  size  and  tinctorial  qualities  of  the 
nucleus,  the  degree  of  granulation  of  the  proto- 
plasm and  the  location  of  the  granules,  appearance 
of  the  undulating  membrane,  length  of  flagellum 
and  shape  of  the  posterior  non-flagellated  end. 


Differentiation. 


TRYPANOSOMIASIS   I^^   MAJ^^. 

Kepreu  in  1898  flrst  found  trypanosomes  in 
the  blood  of  man  in  Algiers  in  eight  cases.  His  ob- 
servations were  passed  over  temporarily.  The  para- 
site bears  his  name  (T.  neprevi).  Again  in  1901 
Forde    discovered    similar    parasites    in    Western 


Trypanoso- 
ma tic  Fever. 


*  Knowledge  is  very  deficient  concerning  the  questions  of 
conjugation  and  sexual  cycles.  An  exception  is  to  be  made  in 
relation  to  halteridium,  a  parasite  of  bird  malaria,  which  is 

a  trypanosomc,   according  to  Scliaudinn.      (See  page  483.) 


486  I\FEVT10\   AM>  IMMrXlTY. 

Africa  (Gambia),  and  since  that  time  a  number 
of  cases  of  "Gambian  fever"  or  trypanosomatic 
fever  in  man  have  been  imported.  In  this  in- 
stance the  parasite  was  called  T.  gamhicnsc  b}^  But- 
ton and  2\  liomlnis  by  Manson.  The  disease  is 
said  to  follow  the  bite  of  a  tsetse-fly  (Glossina 
palpalis).  at  least  in  some  instances.  The  tissues 
around  the  bite  become  inflamed  and  in  from  a 
few  days  to  two  weeks  recurring  attacks  of  fever 
set  in,  and  a  patchy  and  ringed  crythenurtous  erup- 
tion appears  on  the  skin.  Forde  gives  as  the 
chief  clinical  findings  in  his  case:  1,  the  irregular 
intermittent  temperature;  2,  the  edematous  con- 
dition of  the  face  and  lower  extremities ;  3,  the 
rapid  and  variable  pulse  and  respiration,  unac- 
companied by  any  evident  cause ;  4,  loss  of  weight, 
with  marked  debilitj^,  wasting  and  lassitude;  5. 
the  persistence  of  these  symptoms  and  their  re- 
sistance to  treatment.  The  parasites  are  most 
numerous  in  the  blood  at  the  time  of  the  febrilfe 
attacks.  Eecovery  has  not  been  reported. 
Sleeping  Sleeping  sickness  has  been  endemic  in  certain 
districts  of  Africa  for  a  long  time,  and,  although 
confined  to  a  very  limited  district  at  one  time,  it  ap- 
pears now  to  have  extended  to  distant  parts.  Speak- 
ing of  trypanosomatic  fever  and  sleeping  sicloiess 
collectively,  Ruata  says  that  while  originally  con- 
fined to  a  small  rlistrict  in  Western  Africa  between 
the  latitudes  15'  ISTorth  and  15'  South,  it  is  now 
found  one  thousand  miles  up  the  Congo  (Bangola, 
Stanley  Falls)  and  in  East-central  Africa  on  the 
shores  of  the  A^ictoria  Nyanza  Lake.  "ISTow  it  ex- 
tends from  the  mouth  of  the  Katonga  Eiver 
through  Uganda  (1901,  Cook),  Kome  Island. 
Busaga,  Buvuma,  Kavirondo,  Kisumu,  Lumbwa, 


TRYPANOSOMIASIS. 


487. 


Homa,  Kasagiuiga,  Lnsinga  Island,  the  eastern 
shores  of  the  lake,  joining  the  south  of  the  bound- 
ary river  Gori  in  the  Udcmi  district  of  the  Sultina 
of  Obo"  (Kuata). 

Its  extension  supposedly  has  been  facilitated  by 
rapid  transit.  "The  disease  is  most  prevalent 
amongst  the  inhabitants  of  low-lying  shambas  (ba- 
nana and  potato  plantations)  in  places  along  the 
shores  of  the  Victoria  ISTyanza,  or  in  wooded  dis- 
tricts not  far  from  the  water"  (Christy).  Those 
living  on  high  ground  are  much  less  infected  than 
those  living  in  the  low  moist  places  near  water.  A 
great  deal  of  stress  is  laid  on  its  close  association 
with  inland  bodies  of  water. 

It  apparently  has  no  relation  to  sex,  age,  sea- 
sons, food  or  drinking  water,  and  is  related  to  oc- 
cupation only  in  so  far  as  the  occupation  carries 
one  into  the  low  places  mentioned. 

At  one  time  (1891)  Manson  advanced  the  idea 
that  sleeping  sickness  is  caused  by  the  minute 
Filaria  perstans.  It  has  since  developed  that  this 
parasite  occurs  in  70  per  cent,  of  the  natives  in 
certain  districts,  and  that  sleeping  sickness  may 
occur  in  areas  in  which  Filaria  perstans  does  not 
exist;  Manson  has  abandoned  this  view.  A  num- 
ber of  investigators  also  found  cocci  in  the  cerebro- 
spinal fluid,  but  this  occurred  very  rarely  during 
life  and  at  a  late  stage  of  the  disease;  such  organ- 
isms are  probably  secondary  or  agonal  invasions 
in  spite  of  their  rather  frequent  occurrence.  Fur- 
ther investigations  by  Castellani  disclosed  the  pres- 
ence of  a  trypanosome  {T.  castellani)  in  the  cere- 
bro-spinal  fluid  of  a  large  percentage  of  the  cases, 
and  a  little  later  Bruce  found  this  organism  in  all 
the  cases  he  had  examined.     This  observation  has 


Occurrence. 


Trypanosomes 

in-Sleeping 

Sickness. 


488  INFECTION  AND  IMMUNITY. 

been  confirmed  so  many  times  that  the  trypan- 
osome  is  noAv  generally  considered  as  the  cause  of 
the  disease. 
Tsetse  Sleei)iug  sickness  is  not  contagious  in  the  or- 
'"'>'•  dinary  sense,  and  Bruce  furnishes  rather  strong 
evidence  that  it  is  transmitted  by  the  bite  of 
a  tsetse-fly  (Glossina  palpaUs).  The  distribu- 
tion of  the  disease  corresponds  to  the  habitat  of 
this  fly,  and  Bruce  transferred  the  infection  to 
monkeys  by  means  of  flies  which  had  bitten  those 
suffering  from  sleeping  sickness.  Sambon  does 
not  consider  the  experiments  above  criticism. 
Symptoms.  ^^  pronounccd  lethargy  or  somnolence  is  the 
most  striking  clinical  feature  of  the  disease.  "The 
appearance  of  the  somnolent  condition  is  preceded, 
often  for  a  long  time,  by  prodromal  signs,  which 
are  so  characteristic  that  the  patient's  neighbors 
cannot  possibly  be  deceived  as  to  the  fate  that 
awaits  him.  The  victim  complains  of  wealcness, 
langour,  dejection,  disinclination  for  work,  head- 
aches, particularly  localized  over  the  occiput,  a 
sensation  of  weight  in  the  head  and  giddiness. 
His  eyelids  tend  continually  to  close  and  he  has  a 
tendency  to  go  to  rest  at  unusual  hours  of  the  day ; 
for  this  purpose  he  seeks  out  lonely  quiet  spots, 
where  he  spends  a  long  time  in  dozing"  (Scheube). 
For  some  time  he  is  able  to  resist  the  somnolence, 
and  when  aroused  gives  intelligent  answers.  He 
eventually  acquires  an  unsteady  gait  and  walks 
about  like  a  drunken  man.  The  temperature  of 
the  body  appears  to  be  lowered,  although  irregular 
attacks  of  fever  occur.  The  somnolence  gradually 
becomes  more  intense,  the  patient  grows  very  weak, 
the  pulse  small  and  thready,  respiration  difficult, 
the  edema   seen   in  trvausoniatic  fever  is  rather 


TRYPANOSOMIASIS. 


489 


constant,  incontinence  of  the  urine  and  feces  may 
develop;  the  patient  commonly  dies  after  passing 
into  a  state  of  deep  stupor.  Convulsions  and  pa- 
ralyses are  noted;  the  mind  usually  is  clear  when 
the  patient  is  conscious,  although  maniacal  at- 
tacks and  delusions  are  occasionally  noted.  The 
cervical  and  superficial  lymphatics  are  frequently 
but  not  constantly  enlarged.  A  papulo-vesicular 
eruption  is  quite  characteristic  and  persistent  and 
the  skin  becomes  very  dry.  The  incubation  period 
varies  from  six  to  eighteen  months,  and  the  som- 
nolent state  from  three  to  twelve  months.  Eecov- 
ery  rarely  occurs. 

The  essential  anatomic  change  is  meningo-en- 
cephalitis,  the  soft  membranes  being  thickened, 
containing  a  milky  fluid  and  the  vessels  of  the  pia 
and  brain  being  surrounded  by  an  extensive  infil- 
tration of  mononuclear  leucocytes. 


Meningo- 
Encephalitis. 


The  discoverv  of  trypanosomes  in  sleeping  sick-   identity  of  jry- 

•t  -J  i-  J.       o  panosomatic 

Fever  and 
Sleeping 


ness  suggested  that  tryanosomatic  fever  may 
really  represent  the  long  prodromal  stage  of  sleep- 
ing sickness.  This  view  has  been  greatly  strength- 
ened by  a  case  reported  by  Manson  in  which  a 
typical  case  of  tryanosomatic  fever  was  seen  to 
pass  into  typical  and  fatal  sleeping  sickness.  The 
wife  of  a  missionary  in  upper  Congo  was  bitten 
by  a  tsetse-fly,  and  following  an  inflammatory  re- 
action at  the  seat  of  the  bite,  she  developed  and  ran 
a  long  course  of  tryanosomatic  fever.  After  a 
year  and  a  half  to  two  years  of  remittent  attacks 
of  fever,  the  organisms  being  found  in  the  blood 
repeatedly,  she  grew  weaker,  became  somnolent 
and  died  in  a  comatose  condition.  The  anatomic 
changes  at  autopsy  were  typical  of  sleeping  sick- 
ness.   Some  who  are  not  quite  willing  to  accept  the 


Sickness. 


The 
Parasite. 


490  IXFECTION  AM)  IMMU^'ITY. 

unity  of  the  two  diseases  suggest  that  the  sleeping 
sickness  may  have  been  superimposed  on  trypann- 
matic  fever. 

Assuming  that  the  two  conditions  represent  dif- 
ferent stages  of  the  same  disease,  we  would  have 
to  recognize  trypanosomatic  fever  as  the  first  stage 
and  the  letharg}^  of  sleeping  sickness  as  the  second. 
If  this  proves  to  be  correct  the  name  of  T.  neprevi 
should  be  retained  for  the  organism  and  the  other 
names  dropped  (T.  gamhicnse,  T.  hominis,  T. 
castellani) . 

It  is  believed  that  T.  castellani  is  a  distinct 
species  of  trypanosome.  It  is  hardly  possible  to  as- 
sociate it  "s\dth  nagana,  since  sleeping  sickness  and 
nagana  do  not  coincide  in  their  distribution,  and, 
moreover,  the  morphology  and  pathogenicity  of 
T.  castellani  differ  from  that  of  T.  hrucei.  The 
former  is  not  infectious  for  the  "donkey,  ox, 
guinea-pig,  dog,  pup,  goat  and  sheep"  (Kuata). 
T.  castellani  is  from  18  to  25  microns  long  and  2 
to  2.5  broad.  Its  morphology  in  general  is  like 
that  of  other  trypanosomes,  although  there  are 
sufficient  differences  to  establish  its  independence. 
Its  motility  is  rather  slow,  and  in  contrast  to  other 
trypanosomes  it  moves  in  the  direction  of  its  non- 
flagellated  end.  The  failure  to  find  any  distinc- 
tive difference  between  this  organism  and 
T.  neprevi  (T.  gamhiense)  is  an  additional  point 
in  favor  of  the  unity  of  trypanosomiasis  fever  and 
sleeping  sickness. 

TRYPAXOSOMIASIS    IN"    ANIMALS. 

On  account  of  the  prevailing  general  interest  in  the 
subject,  the  more  important  trypanosomatic  infections 
in    animals    and    the    corresponding    parasites    will    be 

sketched  briefly. 


TRYPANOSOMIA  HIH. 


491 


Musgrave  and  Clegg  speak  of  certain  general  symp- 
toms which  are  common  to  surra,  nagana,  nuil  do  cederan 
and  dourine,  as  follows:  "After  an  incubation  period, 
which  varies  in  the  same  class  of  animals  and  in  those  of 
different  species  as  well  as  with  the  conditions  of  infec- 
tion, and  during  which  the  animal  remains  perfectly 
well,  the  first  symptom  to  be  noticed  is  a  rise  of  tem- 
perature, and  for  some  days  a  remittent  or  intermittent 
fever  may  be  the  only  evidence  of  illness.  Later  on  the 
animal  becomes  somewhat  stupid;  watery  catarrhal  dis- 
charges from  the  nose  and  eyes  appear;  the  hair  becomes 
somewhat  roughened  and  falls  out  in  places.  Finally 
the  catarrhal  discharges  become  more  profuse  and  the 
secretion  more  tenacious  and  even  purulent;  edema  of 
the  genitals  and  dependent  parts  appears;  a  staggering 
gait,  particularly  of  the  hind  parts,  comes  on  and  is  fol- 
lowed by  death." 

The  incubation  period  varies  from  a  few  to  several 
days.  Pronounced  anemia  develops,  the  method  of  de- 
struction of  the  erythrocytes  being  unknown.  Lymphatic 
enlargement  is  the  rule,  and  during  the  incubation  period 
the  parasites  probably  undergo  great  proliferation  in  the 
lymph  glands.  It  is  somewhat  characteristic  that  mas- 
sive invasion  of  the  blood  stream  occurs  periodically. 
With  a  paryoxism  of  fever  their  numbers  increase  in  the 
blood,  and  during  the  intermission  they  decrease  and 
may  be  so  few  as  not  to  be  found  microscopically.  Even 
when  few  or  no  parasites  are  found  in  the  circulation, 
however,  the  blood  usually  is  infectious  for  other  ani- 
mals. During  the  intermissions  it  is  possible  that  they 
are  largely  within  the  lymph  glands  or  other  internal 
organs.  The  cause  of  these  variations  is  not  known,  and 
it  can  not  be  said  now  that  they  are  related  to  cycles  of 
development  like  those  of  the  malarial  parasites.  Voges 
suggests  that  they  may  represent  the  establishment  of 
successive  periods  of  temporary  immunity  (mal  de 
cederas ) .  These  are  only  general  features,  and  varia- 
tions occur  in  infections  in  different  animals  and  by  dif- 
ferent parasites. 

Trypanosoma  lewisi,  recognized  in  the  blood  of  the  rat 
by  Lewis  in  1879,  and  given  its  present  name  by  Kent 
in  1882,  infects  wild  rats  throughout  the  world,  and  in 
some  localities  a  very  high  percentage  of  the  animals  are 


General  Symp- 
tomatology. 


Infectiousness 
of  Blood. 


Trypanosomia- 
sis of  Rats. 


492  INFECTIOX  AM)  IMMUNITY. 

infected.  Tlie  parasite  is  readily  found  in  the  peripheral 
blood  (as  from  tl\e  tail),  where  a  large  number  may  be 
present  in  a  single  held  of  the  microscope ;  sometimes, 
however,  prolonged  search  is  necessary  for  their  discov- 
ery. Its  dimensions  vary:  1.4  to  3  microns  in  diameter, 
10  to  2.'5  microns  in  length,  according  to  dill'crcnt  ol)s('rv- 
ers.  It  is  of  lancct-forni.  possesses  a  hnley  granular  cndo- 
plasm  and  a  clear  ectoplasm,  and  from  the  latter  spring 
the  ilagcllum  and  the  undulating  membrane.  "The  for- 
mer (llagcllum)  is  about  as  long  as  the  body  itself; 
it  originates  at  the  posterior  end  of  the  animal  in  a 
grannie-like  structure,  called  the  llagellar  root,  extends 
forward  as  a  marginal  thickening  of  the  undulating 
membrane  and  becomes  free  only  at  the  anterior  end  of 
the  animal  from  which  it  extends  into  the  surrounding 
medium  as  a  flagellum"  (Doflein).  At  its  posterior  ex- 
tremity the  parasite  ends  in  a  sharp  point.  In  its  an- 
terior portion  it  contains  a  strongly  staining  nucleus;  a 
contractile  vacuole  is  not  described.  Its  motility  is,  per- 
haps, more  active  than  that  of  any  other  trypanosome, 
and  in  a  fresh  mount  of  rat's  blood  it  may  move  across 
the  field  so  rapidly  as  to  be  followed  with  difficulty. 

Division  takes  place  by  longitudinal  fission  (rarely 
transverse),  and  by  repeated  division  rosettes  are 
formed. 
Cultivation.  No\^  and  McXeal  succeeded  in  cultivating  this  organ- 
ism artificially  on  a  medium  consisting  of  rabbit's  blood, 
2  parts,  agar,  1  part.  The  growth  occurs  in  the  con- 
densation fluid,  and  the  organisms  were  carried  through 
many  generations.  In  cultures  they  vary  greatly  in  size 
( from  1  to  GO  microns  in  length ) .  "The  existence  of  the 
small  forms  accounts  for  the  fact  that  we  have  repeat- 
edly been  able  to  infect  rats  with  Berkefeld  filtrates  of 
such  cultures."  It  is  remarkable  that  so  many  of  the 
rats  which  harbor  the  parasites  appear  to  be  perfectly 
healthy.  However,  the  animals  not  infrequently  die 
from  the  infection,  and  in  some  instances  fairly  severe 
epidemics  have  been  noted.  The  infection  is  found  also 
in  the  hamster,  a  European  rodent,  and  in  white  rats. 
\'\liite  mice  are  susceptible  to  inoculation    (Doflein). 

Trypanosoma  britcei,  found  by  Bruce  in  1894  in  the 
blood  of  animals  suffering  from  nagana  or  the  tsetse-fly 
disease,  in  Zululand,  is  somewhat  different  morphologi- 


TRYPANOHOMIAHIH.  493 

cally  from  T.  lewisi,  being  more  worm-like  in  form,  hav-  Nagana. 
ing  a  blunt  posterior  extremity,  less  motility  and  greater 
pathogenicity.  "The  undulating  membrane  is  broader 
and  more  plicate,  the  protoplasm  colors  more  easily  and 
more  deeply"  than  in  T.  lewisi.  Its  length  is  said  to 
vary,  depending  on  the  animal  which  harbors  it,  being 
largest  in  the  rat  and  shorter  and  thicker  in  the  dog. 
Its  dimensions  as  given  by  Laveran  and  Mesnil  are  1  to 
\Y2.  by  26  to  27  microns.  Its  structure  is  similar  to  that 
of  T.  lewisi,  containing  a  nucleus  near  the  middle  of  the 
body  and  a  deeply  staining  centrosome  in  the  posterior 
portion  in  or  near  which  the  flagellum  has  its  origin. 
A  contractile  vacuole  lies  anterior  to  the  centrosome. 

Natural  infection  (nagana)  with  this  organism  occurs 
in  horses,  cattle,  mules,  and  also  in  some  wild  animals, 
as  camels,  buffaloes  and  hyenas.  It  is,  however,  a  tropi- 
cal disease,  occurring  chiefly  in  various  parts  of  South 
Africa.  Nearly  all  animals  are  susceptible  to  artifi- 
cial infection  by  the  injection  of  diseased  blood. 

The  distribution  of  nagana  corresponds  with  the  dis-  tsetse 
tribution  of  the  tsetse-fly,  and  Bruce  discovered  that  this  Fly. 
fly,  after  feeding  on  the  blood  of  an  infected  animal, 
transfers  the  disease  to  others  by  biting.  Horses,  asses, 
cattle  and  hogs  were  infected  artiflcially  in  this  way,  but 
man  appears  not  to  be  susceptible.  It  is  assumed,  but 
perhaps  not  definitely  proved,  that  no  other  fly  or  insect 
transmits  the  disease.  Immediately  after  it  has  fed  on 
infected  blood  it  is  capable  of  transferring  the  disease; 
hence,  further  development  of  the  parasite  in  the  tsetse- 
fly  is  not  essential  for  its  continued  infectiousness,  and, 
indeed,  it  is  not  certain  that  any  further  development 
occurs. 

Nagana  presents  a  remittent  or  intermittent  type  of 
fever,  catarrhal  secretion  from  the  nose  and  eyes,  sub- 
cutaneous edema,  particularly  of  the  abdominal  region, 
prepuce  and  posterior  extremities,  roughening  and  shed- 
ding of  the  hair,  marked  emaciation,  weakness  and  ane- 
mia develop,  and  the  animal  dies  in  a  state  of  exhaus- 
tion. The  spleen  is  greatly  swollen,  the  red  corpuscles 
are  diminished  in  number,  and  the  urine  may  be  blood 
stained.  The  parasites  are  found  in  enormous  numbers 
in  the  blood. 

The  disease  is  almost  invariably  fatal.     It  may  last 


494  /.V/'A'('77(>.V  .1\7>  /  1/1/ r\ /'/■)". 

for  weeks  or  months  in  horses,  and  even  much  longer  in 
cattle.  It  occurs  not  infrequently  in  epidemic  form, 
wiping  out  the  horses  and  cattle  of  infected  regions.  In 
wild  animals  it  is  suggested  that  the  disease  may  be 
more  chronic,  and  the  shifting  of  siicli  animals  may 
serve  to  introduce  the  infection  to  new  regions,  but  only 
to  such  regions  as  harbor  the  tsetse-fly. 
Cultivation.  Now  and  McNeal  cultivate  T.  brucei  on  a  medium 
similar  to  that  used  for  T.  leioisi.  The  former  is  more 
exacting  in  its  conditions  for  growth,  preferring  a  me- 
dium containing  blood  and  agar  in  a  ratio  of  two  to  one 
or  three  to  one.  Cultures  were  kept  alive  for  at  least 
one  hundred  days  through  eight  generations,  although 
virulence  was  soon  lost. 
Surra.  Trypanosoma  evansi  is  the  name  given  by  Steele  to  a 
parasite  discovered  by  Evans  (1880),  in  India,  in  the 
blood  of  horses  suffering  from  surra.  It  has  the  same 
general  morphologic  features  as  T.  brucei,  with  dimen- 
sions of  1  to  3.5  or  4  microns  by  20  to  35  microns,  in- 
cluding the  flagellum  ( Musgrave  and  Clegg ) .  It  con- 
tains a  nucleus  and  possibly  a  contractile  vacuole.  The 
whole  posterior  extremity  is  contractile,  according  to 
Musgrave  and  Clegg,  and  this  may  also  be  true  of  other 
trypanosomes.  Its  motility  is  moderate  and  eel-like.  It 
differs  from  the  trypanosome  of  rats  (T.  leicisi)  in  its 
larger  diameter  and  in  its  greater  pathogenicity;  T. 
evansi  is  pathogenic  for  "nearly  all  animals."  It  is 
longer  than  T.  brucei. 

Surra  affects  horses  chiefly,  and  has  caused  immense 
losses  in  India  and  in  the  Philippine  Islands.  In  India 
it  is  certainly  transmitted  by  certain  flies,  and  the  same 
probably  is  true  in  the  Philippines.  Musgrave  and  Clegg 
demonstrated  also  that  fleas  may  be  of  great  importance 
as  carriers.  By  this  means  they  were  able  to  transfer 
the  disease  from  dog  to  dog,  rat  to  rat,  and  rat  to  dog. 
They  frequently  found  the  parasites  in  native  rats  and 
believe  that  this  animal  may  serve  as  a  host  in  which  the 
disease  is  maintained.  Cattle  are  susceptible  to  infec- 
tion, but  the  disease  is  less  malignant  in  them  and  runs 
a  long  course;  hence,  they  may  be  an  important  factor 
in  maintaining  an  epidemic.  The  disease  is  also  trans- 
mitted from  horse  to  horse.     In  India,  camels,  elephants 


TliVrANOSOlMIAHIH. 


495 


and  buffaloes  also  suffor  from  the  disease.     Surra  resem- 
bles nagana  in  its  clinical  and  anatomic  aspects. 

Doflein  gave  the  name  of  Trypanosoma  equiperdum  to  Q^^fi^^ 
an  organism  described  by  Rouget  in  horses  and  asses 
suffering  from  dourine.  Laveran  and  Mesnil  call  it  T. 
rougetii.  According  to  Rouget,  the  parasite  resembles 
T.  brucei  closely.  Doflein  ( 1901 )  states  that  a  nucleus 
and  vacuole  have  not  been  seen.  Dourine  occurs  in 
Algiers,  southern  France,  Navarre  and  in  the  Pyrenees 
districts  of  France  and  Spain.  The  infection  is  trans- 
mitted by  coitus  and  is  limited  largely  to  animals  which 
are  used  for  breeding.  Ulcerations,  particularly  of  the 
genitals,  are  characteristic.  That  it  is  not  transmitted 
by  insects  may  be  due  to  the  absence  of  suitable  insects 
from  these  localities.  The  identity  of  dourine  vpith 
surra  or  nagana  is  not  yet  determined.  It  is  said  to  be 
more  chronic  than  surra.  Doflein  recognizes  the  organ- 
ism as  an  independent  parasite.  Infection  may  be  trans- 
ferred to  dogs,  white  mice  and  other  animals. 

Trypanosoma  equinum    (Voges)    or   T.   elmassianii   is    Mai  de 
the  parasite  found  in  mal  de  cederas,  a  disease  of  horses    Cederas. 
in  South  America,  resembling  surra,  nagana  and  dourine. 

Two  different  species  have  been  found  in  the  blood  of  infections  of 
South  African  cattle:  T.  theileri  (Bruce,  1902)  and  T.  Other  Animals 
transvaaliense  (Laveran  and  Mesnil,  1902).  The  char- 
acteristic feature  of  the  latter  is  the  location  of  the 
centrosome  near  the  nucleus  near  the  center  of  the  para- 
site. The  following  trypanosomes  are  found  in  fish: 
T.  cohitis,  T.  carassii,  T.  remaJcii,  T.  solecB,  T.  borrelUi; 
the  folloAving  in  birds:  T.  avium,  T.  eberthii.  T.  balbianii 
occvirs  in  oysters,  T.  rotatorium  in  frogs. 

Between  various  animals  and  the  different  try-  immunity 
panosomes  a  number  of  exainples  of  natural  im- 
munit}^  are  known.  The  extent  to  which  man  is 
susceptible  to  sleeping  sickness  is  not  known,  but 
since  the  disease  may  occur  in  Europeans  as  well 
as  in  native  Africans,  it  is  probable  that  suscepti- 
bility is  general.  Laveran  and  Mesnil  state  that 
sheep,  deer  and  cattle  which  have  recovered  from 
nagana  have  an  active  immunity  to  the  disease, 


4!)G  IM'KCTfOX    AM)    niMlMTY. 

•  and  it  is  thought  that  tlio  imiminity  of  some  ani- 
mals (e,  g.,  cow)  may  be  increased  by  injecting 
infected  blood.  Koch,  and  also  Schilling,  have  at- 
tempted to  render  trypanosomas  suitable  for  vacci- 
nation by  passing  them  through  asses,  and  a  cer- 
tain degree  of  success  was  reported.  The  serums 
of  actively  immunized  animals  do  not  exert  a  pro- 
nounced protective  or  curative  action,  although 
they  may  in  some  instances  j^rolong  the  incubation 
j)6riod.  Human  serum  has  a  certain  protective 
and  curative  power  for  rats  and  mice  which  have 
been  inoculated  with  the  parasite  of  nagana.  In 
some  instances  immune  and  normal  serums  kill 
trypanosomes,  as  shown  by  rapid  loss  of  mobility. 
'Trypanroth."  A  most  interesting  bit  of  experimental  therapy 
is  that  of  Ehrlich  and  Sachs  in  curing  and  pro- 
tecting mice  against  mal  de  ccderas  by  injecting 
and  feeding  "trypanroth,"  a  sj-nthetic  dye.  The 
dye  was  less  efficient  in  experimental  nagana  and 
in  trypanosomatic  infections  of  rats,  guinea-pigs 
and  dogs.  Among  hundreds  of  other  dye-stuffs 
no  other  was  effective.  The  immunity  and  cure 
established  in  this  way  is  very  temporary  and  is 
to  be  referred  to  a  reaction  caused  in  the  body 
rather  than  to  a  direct  effect  on  the  parasites..  The 
latter  are  not  killed  by  the  dye  in  test-tube  experi- 
ments. "One  may  conceive  of  the  action  of  try- 
panroth in  this  way,  that  as  a  result  of  a  fresh 
injection  of  the  dye  a  reaction  takes  place  in  the 
animal's  body,  which  leads  to  the  death  of  the 
trypanosomes;  the  reaction  products  possess  only 
a  temporary  character  and  cease  to  be  formed  as 
soon  as  the  dye  is  disposed  of." 

Laveran  reports  a  favorable  influence  on  try- 
panosomiasis in  mice  and  rats  by  a  combined  treat- 
ment with  sodium  arsenite  and  "trypanroth." 


PYROPLAmiOHlH. 


497 


Spontaneous  agglutination  and  agglutination  by 
normal  and  immune  serums  have  been  described. 
At  the  present  time  agglutination  is  of  no  value 
from  the  standpoint  of  diagnosis, 

III.     ''spotted    fever"    of    the    rocky    MOUNTAIN" 
STATES. 

In  the  valley  of  the  Bitter  Eoot  Eiver  of  Mon- 
tana, and  in  certain  sections  of  Idaho,  Wyoming 
and  Washington  an  acute  febrile  disease,  known 
in  those  localities  as  sjootted  fever,  is  encountered 
in  the  spring  months.  The  disease  is  defined  by 
Maxey  as  "an  acute,  endemic,  non-contagious,  Irat 
probably  infectious,  febrile  disease,  characterized 
clinically  by  a  continuous  moderately  high  fever, 
severe  arthritic  and  muscular  pains,  and  a  pro- 
fuse petechial  or  purpural  eruption  in  the  skin, 
appearing  first  on  the  ankles,  wrists  and  forehead, 
but  rapidly  spreading  to  all  parts  of  the  body." 
(Cited  by  Stiles.) 

In  1902-03,  Wilson  and  Chowning  studied  many 
cases  of  the  disease  in  Montana,  and  described  as 
the  cause  a  protozoon  organism  which  they  con- 
sider as  a  pyroplasma  {Pyroplasma  liominis).  The 
organism  is  a  hematozoon,  occurring  within  the 
erythrocytes.  Young  cells  resemble  the  "hyaline 
bodies"  of  malaria,  are  of  ovoid  shape,  1  micron 
thick  and  1  to  2  microns  long,  and  usually  occur  in 
pairs,  but  sometimes  in  numbers  of  4  to  16,  within 
an  erythrocyte.  The  smaller  ends  of  pairs  often 
are  directed  toward  each  other,  and  they  may  be 
connected  by  a  fine  filament.  They  occur  both  in 
the  red  corpuscles  and  in  the  plasma.  As  they 
grow  larger,  two  to  three  by  three  to  five  microns, 
only  one  parasite  usually  is  found  within  an  ery- 
throcyte, and  in  this  stage  they  show  active  ame- 


Limited 
Occurrence. 


Pyroplasma 
Homfnis. 


498 


INFECTIOX    AXD    IMMUNITY. 


Transmission 
by  Ticks. 


Intermediate 
Host. 


bold  movement  with  tlic  formation  of  pseudopodia. 
Eventually  they  assume  a  spherical  form  in  fresh 
preparations,  'i'hey  ^vere  al)le  to  transfer  the  in- 
fection to  rabbits  by  tlie  inoculation  of  infected 
blood. 

After  identifying  the  oi'ganisni  as  a  pyroplasma 
and  having  in  mind  the  part  that  ticks  play  in  the 
transmission  of  Texas  fever,  and  perhaps  pyroplas- 
niosis  in  other  animals  (horse,  sheep,  dog),  Wilson 
and  Cho\vning  directed  their  attention  to  the  ques- 
tion of  tick  bites  in  those  who  become  infected. 
It  developed  that  of  the  23  cases  examined  in  1903 
all  had  been  bitten  by  ticlcs,  and  fourteen  had  been 
bitten  in  from  two  to  eight  days  before  the  onset 
of  the  disease.  They  concluded  that  the  disease  is 
transmitted  in  this  manner. 

They  also  searched  for  some  other  host  than 
man,  in  which  the  parasites  might  flourish  contin- 
uously and  constitute  a  source  of  infection  for  the 
ticks.  This  tliey  believe  was  found  in  a  certain 
gopher  {Spcnnophilus  columhianus) .  On  the  west 
side  of  the  river — that  side  in  which  the  disease 
attacks  man — they  found  the  erythrocytes  of  about 
20  per  cent,  of  the  gophers  infected  with  a  parasite 
similar  to  that  found  in  man.  On  the  other  hand, 
the  blood  of  sixty-two  gophers  from  the  uninfected 
side  of  the  river  showed  no  parasites.  "Early  in 
the  spring  the  spermophile  is  said  to  harbor  great 
numbers  of  ticks."  Similar  parasites  Avere  found 
in  no  other  species  of  animals. 

Stiles,  in  later  investigations,  could  not  confirm 
the  results  of  Wilson  and  Chowning,  being  unable 
either  to  find  the  parasites  which  they  described  in 
man,  or  to  accept  the  tick-gopher  hypothesis.  Fur- 
ther investigation  of  this  disease  is  needed. 


PYR0PLASM08I&. 


49!) 


The 
Parasite. 


TEXAS  FEVER. 

Texas  fever  of  cattle  may  be  considered  briefly  as  a 
well-established  example  of  pyroplasmosis. 

Th.  Smith  and  Kilbourne  (1893)  discovered  a  pear- 
shaped  protozoon  (Pyroplasma  bovis) ,  which  occurs  in 
pairs  in  the  erythrocytes  of  infected  cattle.  The  para- 
site measures  from  2  to  4  microns  long  by  1.5  to  2 
microns  broad,  the  smaller  ends  of  the  pairs  lying  in 
apposition.  The  organisms  have  a  rapid  but  rather  coarse 
ameboid  movement.  About  1  per  cent  of  the  corpuscles 
are  invaded  ordinarily,  but  in  fatal  cases  the  proportion 
may  rise  from  5  to  10  per  cent.  The  method  of  prolifera- 
tion of  the  parasite  has  not  been  followed  out  definitely. 
According  to  Smith  and  Kilbourne,  numerous  minute 
motile  forms  (coccus-like  bodies)  penetrate  the  corpus- 
cles and  eventually  reach  the  pear-shaped  form.  The 
breaking  up  of  the  adult  pear-shaped  parasites  into  such 
small  forms  has  not  been  observed. 

A  characteristic  symptom  of  Texas  fever  is  the  pro- 
nounced hemoglobinuria  which  has  given  to  the  disease 
the  additional  name  of  hemoglobinuric  fever. 

The  disease  is  transmitted  by  means  of  a  tick  (Boophi- 
lus  hovis) .  The  six-legged  larvae  fill  themselves  with 
blood,  and  in  about  eight  days  have  been  changed  into 
eight-legged  nymphse.  In  eight  days  more  they  have 
changed  into  fully-formed  sexual  animals,  and,  after 
filling  themselves  with  blood  and  after  having  been  im- 
pregnated, they  drop  off  the  cattle  and  lay  their  eggs. 
The  eggs  in  from  3  to  4  weeks  have  again  gro\vn  into 
larvse,  which  are  then  ready  to  attach  themselves  to 
cattle  ( cited  from  Kossel ) .  Inasmuch  as  infected  ticks 
transmit  the  parasites  to  their  offspring,  the  bites  of  the 
larvse  are  able  to  give  rise  to  the  disease  in  cattle.  A 
mature  tick  may  deposit  from  2,000  to  4,000  eggs.  It 
has  not  been  possible  to  transmit  the  disease  to  other 
species. 

The  disease  is  endemic  in  the  southwestern  states,  Transmission 
and  the  cattle  in  that  region  are  supposed  to  acquire  an 
immunity  similar  to  that  described  by  Koch  in  relation 
to  malaria.  Presumably  the  cattle  first  acquire  the  dis- 
ease when  they  are  young,  and  those  which  withstand  it 
show   resistance   to   the   infection   in   later   life.      Cattle 


500  INFECTION    AND    IMMrXITY. 

from  uninfected  districts  are  more  susceptible  than  those 
coming  from  localities  in  which  the  disease  is  endemic, 
and  the  latter  even  when  apparently  healthy  may  intro- 
duce the  disease  into  new  herds.  This  is  done  through 
transportation  of  the  ticks. 

Partialh'  successful  attempts  at  active  immunization 
have  been  made,  and  in  Australia  this  is  practiced  on 
a  fairly  extensive  scale.  Five  to  ten  cubic  centimers  of 
blood,  taken  from  an  infected  animal,  during  the  course 
of  the  disease  or  after  recovery  has  been  established,  are 
injected  into  non-immune  cattle.  The  disease  is  thereby 
reproduced  in  the  latter  with  typical  parasites  in  the 
blood.  If  the  blood  is  taken  from  animals  which  have 
recovered,  a  milder  infection  results  than  when  the  blood 
of  an  actively  infected  animal  is  used  (Pound,  cited  by 
Kossel).  The  resulting  immunity  is  not  an  absolute  one, 
however,  and  the  percentage  of  mortality  is  fairly  high. 
According  to  Dodson,  the  serum  of  animals  which  have 
completely  recovered  has  no  protective  power  for  other 
animals. 

For  prophylaxis  it  is  important  to  free  the  cattle 
from  ticks  (as  by  an  oil  bath)  and  to  avoid  infected 
fields.  If  cattle  are  kept  from  an  infected  pasture  for 
two  years,  the  ticks  die  out  very  largely   (Morgan). 

IV.    AMEBIC    DYSENTERY. 

Amebae.  Aiiieba?  ai'c  uiiiccUular  animal  organisms  -whiL-li 
contain  one  or  more  nuclei,  a  "contractile"  vacuole. 
a  granular  endoplasm  and  a  tougher  more  hyaline 
ectoplasm,  having  the  power  of  locomotion  by 
means  of  pseudopodia  or  by  a  gradual  flowing  for- 
ward of  the  cytoplasm.  They  nourish  themselves 
by  digesting  bacteria  and  other  lower  organisms  or 
solid  particles  of  decaying  matter,  which  they  in- 
gest after  the  manner  of  phagocytes.  They  pro- 
liferate by  division  of  an  adult  cell  into  two  daugh- 
ter cells,  and  certain  of  them  reach  a  cystic  stage 
in  which  hundreds  of  endospores  are  formed 
{A.meha  proteus).  Some  of  them  utilize  higher 
animals  as  hosts  only  occasionally,  while  others 


AMEBIC  DYSENTERY.  501 

are  known  only  as  parasites.  They  frequently  are 
encountered  in  the  intestines  of  mice,  frogs  and 
other  animals. 

Amebge  are  widely  distriljuted  in  nature,  exist-  Distribution. 
ing  to  the  depth  of  3  meters  in  tropical  soils,  in 
the  water  of  springs  and  wells  and  practically  all 
surface  waters  (hot  countries),  and  in  stagnant  or 
sluggish  waters  in  higher  altitudes.  They  exist  on 
hay,  fruits  and  vegetables  of  all  kinds,  especially 
those  grown  on  or  near  the  earth;  e.  g.,  beets  and 
lettuce. 

Encystation  takes  place  under  certain  unfavor-  Resistance. 
able  conditions,  and  in  this  condition  the  parasites 
"withstand  a  temperature  of  — 15°  C.  for  twenty- 
five  days  (Musgrave  and  Clegg),  and  desiccation 
for  ten  to  fifteen  months.  A  temperature  of  50°  C. 
kills  the  vegetative  and  encysted  forms.  Sunlight 
for  three  hours  and  the  a;-ray  kill  them  readily  in 
the  vegetative  form,  but  not  so  readily  when  they 
are  encysted.  Most  chemical  bactericides  destroy 
them,  although  they  show  a  particular  resistance  to 
alkalies,  even  20  per  cent.  ISTaOH  (Frosch),  and 
strong  acids.  They  resist  the  action  of  0.3  per 
cent.  HCl,  i.  e.,  the  acidity  of  the  stomach  con- 
tents. Quinin  (1/3500  of  the  hydrochlorate)  is 
strongly  germicidal  for  Ameha  coU. 

Under  artificial  conditions  amebse  proliferate  Cultivation. 
in  the  presence  of  other  micro-organisms,  and 
suitable  mixtures  they  may  be  kept  alive  in- 
definitely on  slightly  alkaline  bouillon  agar. 
The  only  condition  in  which  ameba  are  found 
unassociated  with  bacteria  is  in  the  liver  ab- 
scesses which  occur  as  a  complication  of  amebic 
dysentery.  It  is  true  that  the  bacteria  may  have 
been  present  original^,  but  in  their  absence  it  is 


502 


IXFECriON    AND    IMMUNITY. 


supposed  tliat  onzvines  noniially  present  in  the 
liver  stimulate  the  growth  ami  proliferation  of  the 
parasites.  Amebae  show  a  peculiar  selective  property 
for  certain  bacteria,  although  tiieir  affinities  may 
be  gradually  moililled.  Aincba  coU  apparently  pre- 
fers those  organisms  which  Hourish  in  the  human 
intestines  (B.  coll,  B.  typhosus,  Sp.  cholerce,  Staph, 
pyog.  aureus).  Almost  any  strain  will,  however, 
grow  with  a  variety  of  bacteria.  Growth  occurs 
only  on  the  surface  of  the  agar  plates.  When  a 
pure  strain  of  ameba  is  grown  with  a  single  species 
of  bacterium  the  culture  is  spoken  of  as  a  "pure 
mixed  culture." 

Amebic  dysentery  is  primarily  a  disease  of  the 
tropics,  where  the  natural  conditions  are  favorable 
for  the  growth  of  the  amebae  and  their  conveyance 
to  man. 

First  found  by  Lambl  (18G0),  then  by  Cunning- 
ham and  Lewis  (1870),  the  organisms  were  de- 
scribed more  accurately  and  given  the  name  of 
Ameba  coli  by  Losch  (1875).  Losch  recognized 
them  as  the  cause  of  a  chronic  form  of  dysentery, 
but  it  was  Kartulis,  in  particular,  who  found  the 
amebte  constantly  in  the  discharges  and  ulcers  of 
the  disease,  and  also  in  the  liver  abscesses  which 
accompany  the  infection.  Since  ameba?  demand 
the  presence  of  living  bacteria  for  their  growth. 
Pathogenicity,  their  independent  pathogenic  nature  has  been  ques- 
tioned by  many  who  assume  that  the  bacteria  are 
the  primary  agents  in  causing  the  intestinal  lesions 
and  that  the  amebae  are  only  incidental  or  second- 
ary factors.  Many  others,  and  particularly  Mus- 
■  grave  and  Clegg,  consider  that  amebae  have  essen- 
tial pathogenic  properties  and  are  the  primary 
agents  in  producing  ameljic  dysentery.  By  the 
feeding  of  encvsted  cultures  grown  with  other  or- 


Ameba 
Coli. 


AMEBIC  DYSENTERY. 


503 


ganisms,  Musgravc  and  Clegg  reproduced  the  dis- 
ease, typically  in  many  monkeys.  In  one  instance 
the  amebse  were  fed  in  conjunction  with  cholera 
vibrios;  typical  dysentery  developed  and  during 
the  course  of  the  disease  the  vibrios  disappeared 
from  the  stools.  The  vibrio  alone  proved  to  be 
non-pathogenic  Avhen  fed  to  monkeys,  and  on  this 
account  they  held  the  amebte  to  be  the  sole  cause 
of  the  dysentery. 

The  principal  lesions  occur  in  the  large  intes- 
tine, in  which  are  found  round  or  oval  ulcers  with 
infiltrated  or  undermined  edges.  The  ulcers  may 
increase  in  size,  or  coalesce  with  others,  and  cause 
the  sloughing  of  large  areas  of  the  mucosa  or  even 
of  the  muscular  coats.  The  organisms  are  found 
in  the  intestinal  contents,  on  the  surface  of  the 
ulcers,  in  the  infiltrated  base  and  edges,  and  in  the 
underlying  tissues.  They  have  been  found  as- 
sociated with  both  chronic  and  acute  appendi- 
citis. Amebic  liver  abscesses  are  not  infrequent 
in  those  regions  in  which  the  disease  is  endemic. 
The  organisms  probably  extend  to  the  liver  from 
the  intestines  through  the  lymphatic  or  portal 
vessels.  Not  infrequently  the  association  of  the 
amebae  with  bacteria  is  missed  in  the  abscesses, 
and  in  these  instances  a  "cold^'  abscess  containing 
much  necrotic  material  and  detritus  is  produced. 
If  contaminated  with  bacteria  the  abscesses  have 
a  more  purulent  character. 

Suitalale  prophylaxis  against  amebic  infection  is 
suggested  by  the  known  distribution  of  these  or- 
ganisms. Of  principal  importance  is  the  use  of  fil- 
tered or  boiled  waters  and  the  avoidance  of  un- 
cooked vegetables  in  regions  in  which  the  disease 
is  endemic,  as  in  the  Philippine  Islands. 


Lesions 


Prophylaxis 


504  IXFECTIOX    AXD    niMVMTY. 

inim«nity.  Froiii  thc  fact  tliat  foreigners  going  into  tropical 
countries  are  more  susceptible  to  infection  than  the 
natives,  it  is  concluded  that  the  latter  have  some 
natural  (or  acquired)  inuuuuity  to  the  disease. 
Children  are  said  to  be  less  susceptible  than  adults 
and  in  them  the  disease  yields  to  treatment  more 
easily.  There  is  no  serum  therapy  for  the  infec- 
tions. The  salts  of  quinin  in  strengths  of  1-1500 
to  1-750  are  aiuebieidal  Avlion  injected  into  the 
colon. 

V.    SAHCOSrORIDIA. 

Morphology.  Sarcosporidia  are  unicellular  parasites  which  are 
found  within  the  muscle  cells  of  some  animals,  but 
very  rarely  in  man.  They  are  more  or  less  tubular 
or  oval  in  shape  and  are  frequently  referred  to  as 
Miescher's  tubules.  Their  size  varies  greatly  and 
certain  species  may  reach  a  length  of  two  centi- 
meters. When  well  developed  they  possess  two 
capsules — a  dense  outer  capsule,  which  is  perfor- 
ated with  minute  canals  (?)  directed  toward  the 
center  of  the  parasite,  and  an  inner  thin  hyalin 
membrane.  Both  represent  differentiated  ecto- 
plasm (Doflein).  The  endoplasm,  even  in  young 
cells,  gives  rise  to  numerous  small  nucleated 
spheres  (pansporoblasts),  which  increase  in  size 
and  each  of  which  eventually  becomes  multinu- 
cleated and  forms  numerous  kidney  or  sickle- 
shaped,  nucleated  sporoblasts.  Each  sporoblast 
finally  gives  rise  or  is  changed  into  a  well-charac- 
terized spore  with  a  membrane  and  a  nucleus. 
This  process  takes  place  first  in  the  central  part 
of  the  parasite,  but  eventually  extends  to  the  ends 
as  well.  The  central  part  of  the  old  parasites  con- 
tains only  the  empty  network  of  endoplasm,  the 


/SM  liCOHPORlblA.  505 

spores  having  disappeared,  and  a  section  at  this 
point  strongly  resembles  that  of  a  tubule. 

The  parasites  are  nourished  through  osmosis. 
None  of  the  forms  have  definite  motility.  When 
the  parasite  outgrows  the  muscle  cell  which  con- 
tains it,  it  is  freed  and  becomes  an  intercellular 
parasite.  Rather  vague  references  are  made  to 
tumor-like  formation  as  a  consequence. 

Sarcosporidia  have  been  found  only  in  verte-  occurrence. 
brates,  particularly  in  mammals;  most  often  in 
sheep  and  hogs,  but  also  in  the  horse,  ox,  mouse, 
rat.  The  muscles  adjacent  to  the  alimentary  tract 
are  involved  principally  (esophagus,  intestines, 
diaphragm  and  abdominal  muscles)  and  on  this 
account  it  is  supposed  that  infection  takes  place 
through  the  intestines.  The  exact  method  of  in- 
oculation is  not  known. 

Sarcocystis  lindemanni  (Sarcocystis  liominis  or 
Gregarina  lindemanni)  is  the  only  sarcosporidium 
definitely  identified  in  man.  The  parasites  were 
as  large  as  1.6  millimeters  long  and  170  microns 
broad.  They  possessed  a  thin  capsule,  thickened 
at  the  ends.  The  spores  were  banana-shaped  and 
eight  to  nine  microns  long.  The  organisms  were 
found  in  the  muscles  of  the  larynx. 

VI.    BALANTIDIUM  COLI. 

B.  Co'li  is  an  infusorian  (ciliate),  with  a  more 
or  less  oval  body,  mouth  opening  and  a  short 
pharynx,  is  covered  rather  uniformly  with  short 
cilia,  and  presents  longitudinal  striations.  It  con- 
tains a  bean-shaped  chief  nucleus  and  a  secondary 
nucleus  and  two  vacuoles  on  the  right  side.  It  meas- 
ures 70-100  microns  in  length  and  50-70  in 
breadth.     Proliferation  is  through  simple  division. 


506  INFECTION    AXD    IMMUNITY. 

■  Conjuuation  ha?  beeu  noted.  Involution  cysts  are 
splierioal  and  surrounded  b}'  a  dense  membrane. 
Pathogenic  The  parasite  is  found  in  the  intestines  of  the  hog 
Significance,  ^^g  ^^.^^l  as  in  num,  and  the  former  may  be  its  nor- 
mal host.  It  occurs  also  in  sewage  waters  and  has 
been  found  in  drinking  water.  Infections  have 
been  noted  in  those  having  nothing  to  do  Avith  hogs. 
The  organisms  may  reach  the  intestines  of  man  in 
an  encapsulated  state  (  ?) .  It  is  found  in  diar- 
rheal conditions  in  man  rarel}^,  and  the  question 
is  still  open  as  to  wdiether  the  parasite  is  able  to 
cause  enteritis  independently  or  whether  it  merely 
aggravates  and  prolongs  an  enteritis  due  to  other 
causes. 

The  cecum  and  colon  show  the  principal  changes 
at  autopsy,  and  are  of  an  inflammatory  and  ulcera- 
tive nature. 

A  smaller  species,  B.  minutuin,  has  also  been 
oliserved  in  the  intestines  of  man. 

VII.    CERCOMONAS  INTESTINALIS. 

Morphology.  This  Organism  is  small  and  colorless,  the  form 
spherical  or  oval.  The  single  flagellum  is  for  the 
most  part  very  large  and  is  situated  at  the  anterior 
end  (in  the  direction  in  which  the  parasite 
moves)  ;  the  posterior  end  is  long  drawn  out  and 
is  subject  to  changes  in  form.  Sharp  pseudopodia 
are  sometimes  formed.  The  nucleus  lies  in  the 
anterior  half  of  the  body,  and  either  here  or  on  the 
sides  are  one  or  more  vacuoles.  A  mouth  opening 
is  not  differentiated,  but  at  the  base  of  the  flagel- 
lum food  is  taken  in  at  a  particular  point  through 
a  vacuole.  Proliferation  takes  place  through  con- 
jugation, binary  division  and  the  formation  of 
■swarm  spores  (?)  within  encysted  forms.  They 
abound  in  fresli  water  and  in  infusions  of  2:rasses. 


TRICHOMONAS. 


507 


The}'  are  not  of  great  parasitic  importance,  al-  significance, 
though  cercomonas  has  been  found  in  the  intes- 
tines, especially  in  inflammatory  conditions  (chol- 
era, typhoid),  in  pulmonary  gangrene,  putrid  plu- 
.ritis,  and  several  forms  have  been  observed  in  other 
animals. 

It  is  not  yet  certain  that  cercomonas  may  be  an 
independent  cause  of  enteritis. 

VIII.     TRICHOMOISrAS. 

Eather  small,  of  a  general  pear-shape,  rounded  Morphology. 
or  pointed  anterior  end,  and  possessing  three  or 
four  long  flagella.  When  only  three  flagella  are 
present  an  undulating  membrane  surrounds  the 
body  like  a  spiral  beginning  at  the  base  of  the 
flagella  and  may  prolong  itself  into  a  flagellum. 
The  posterior  extremity  is  moderately  pointed,  a 
nucleus  lies  in  the  anterior  end,  and  toward  the 
posterior  are  several  non-contractile  vacuoles. 
Methods  of  proliferation  unknown  (Doflein). 

Two  species  are  found  in  man.  Trichomonas  species. 
vaginalis:  possesses  three  flagella  and  an  undu- 
lating membrane,  and  is  of  large  size  (15-35  mi- 
crons in  length).  It  is  found  in  the  vaginal  mu- 
cus, when  of  acid  reaction,  in  a  large  percentage  of 
women  (Dolflein),  particularly  in  vaginal  catarrhs. 
It  disappears  in  an  alkaline  reaction. 

Trichomonas  hominis  s.  intestinalis:  also  pos- 
sesses three  flagella  and  an  undulating  membrane, 
but  is  smaller  than  T.  vaginalis.  It  is  found  as  a 
parasite  in  the  human  intestines,  particularly  in 
diarrheas  (typhoid,  cholera,  mucous  colitis,  etc.,) 
.and  inhabits  especially  the  upper  and  middle  por- 
tions of  the  intestines.  It  is  evacuated  in  consid- 
eral  numbers  following  administration  of  cathar- 
tics.   It  appears  not  to  be  of  much  pathogenic  sig- 


508  INFECTIOX    A.\l>    IMMUMTY. 

nilifanoo,  but  tiiuls  in  the  liquid  stools  and  in  an 
alkaline  reaction  conditions  ^vhich  favor  its  prolif- 
eration.    It  may  be  transmitted   as  a  contagion 
(Ejv^tein). 
Other       Otlier  species  of  trichomonas  occur  in  the  intes- 

riagellates.      .  n    i-nc  ,  ^ 

tines  ot  diiierent  animals. 

Other  less  important  flagellates  are:  Lamhlia 
intesiinalis,  found  in  the  intestines  of  many  ani- 
mals and  in  man  in  Germany,  Italy,  Russia  and 
Sweden;  Bodo  urinarius  [Cystomonas  urhiarius. 
Plagiomonas  urinaria),  found  in  the  urine  in  cys- 
titis (Kiinstler). 

IX.    COCCIDIOSIS. 

Coccidia  are  essentially  cell  parasites,  preferring 
the  epithelial  cells  of  the  intestines  and  liver,  al- 
though they  may  be  carried  to  other  organs.  They 
have  an  alternating  asexual  and  sexual  cycle  of 
development.  The  3'oung  sickle-shaped  and  nu- 
cleated sporozoite  penetrates  an  epithelial  cell, 
grows  in  size,  and  the  nucleus  subdivides  many 
times  to  form  new  young  cells,  which  eventually 
escape  again  as  sickle-shaped  sporozoites.  This 
asexual  process  is  called  schizogony.  Several  stages 
of  schizogony  may  follow  successively,  but  event- 
ually the  organisms  lose  their  proliferative  power 
unless  they  are  fortified  by  a  sexual  cycle.  In  the 
sexual  cycle  (sporogony)  some  of  the  sporozoites 
become  differentiated  into  larger  granular  cells 
(female)  and  others  into  smaller  cells  (male). 
Of  these  two  cells  the  male  eventually  divides  into 
many  flagellated  microgametes,  each  of  which  is 
al)le  to  penetrate  and  fertilize  a  female  cell  (macro- 
gamete).  The  female  cell  then  forms  a  capsule, 
becomes  an  oocyst,  divides  into  sporoblasts,  each 
of  which  eventually   forms   sickle-shaped   spores, 


Life  Cycles. 


L'OaCIIJIOHIH. 


oOO 


which  when  liberated  are  again  called  sporozoites. 
Several  species  are  recognized,  depending  on  the 
number  of  spores  formed  by  the  oocyst.  In  some 
instances  the  spore  formation  takes  place  in  the 
outer  world,  and  when  the  oocysts  are  ingested  the 
sporozoites  are  liberated. 

Goccidvum  cuniculi  s.  oviforme  is  a  frequent 
parasite  in  the  intestines  and  liver  of  the  rabbit, 
occurs  occasionally  in  the  same  organs  in  man  from 
association  with  rabbits  (?),  and  causes  a  hemor- 
rhagic dysentery  in  the  cattle  of  some  countries 
(Switzerland).  Horses,  goats  and  swine  may  also 
be  infected. 

Spore  formation  takes  place  outside  the  host. 
The  oocyst'  is  discharged  in  the  feces  and  produces 
four  spores,  each  of  which  forms  two  sporozoites. 
A  new  host  is  infected  by  the  ingestion  of  spores. 

Diarrhea  and  emaciation  result  from  infection 
of  the  intestines,  and  in  the  liver  cheesy  nodules 
(coccidia  nodules)  are  formed,  containing  para- 
sites, degenerated  cells  and  proliferated  epithe- 
lium. A  papillomatous  proliferation  of  the  epi- 
thelium of  the  bile  passages  and  intestines  may  be 
produced. 

Coccidium  higeminuriij  a  coccidium  in  which 
the  oocyst  divides  into  two  spore-containing  cysts, 
has  been  found  in  man  several  times. 


Species. 


Results  of 
Infection. 


GROUP  VI.    DISEASES  OF  DOUBTFUL  OR 
UXKXOWX   ETIOLOGY. 


Negri. 


I.      II  ^■|>l;()l•lln|•,lA. 

Following  the  investigations  of  Pasteur,  in 
which  it  was  found  that  the  virus  of  hydrophobia 
exists  in  the  central  nervous  system  in  pure  cul- 
ture, the  conditions  seemed  favorable  for  the  dis- 
covery of  the  specific  agent.  As  in  the  case  of 
many  other  diseases,  various  bacilli,  cocci,  yeasts 
and  so-called  2>i'otozoa  have  been  dcseriljcd  as  the 
cause,  but  satisfactory  proof  of  their  etiologic  role 
has  not  been  provided. 
Bodies  of  Among  the  recently  described  parasites  (  ?)  cer- 
tain protozoon-like  bodies  (Negri  bodies)  found 
by  jSTegri  in  the  ganglionic  cells  are  of  a  suggestive 
nature.  Their  average  diameter  is  about  five  mi- 
crons, l)ut  it  varies  between  one  and  twenty-seven 
microns.  They  possess  a  "round,  oval,  elliptical, 
or  coarse  triangular  form"  (Marx),  are  differen- 
tiaterl  into  a  central  granular  and  a  peripheral 
structure  and  may  be  surrounded  by  a  doubly- 
contoured  membrane.  Negri  considers  these  bod- 
ies specific  for  hydrophobia  and  reliable  as  a  basis 
for  anatomic  diagnosis.  They  are  found  particu- 
larly in  the  pyramidal  cells  in  the  cornu  Ammonis, 
the  cells  of  Purkinje  in  the  cerebellum,  and  the 
large  cells  of  the  cerebral  convolutions.  Many  oth- 
ers have  confirmed  the  findings  of  Negri.  Against 
the  hypothesis  that  these  bodies  are  the  cause  of 
hydrophobia,  the  following  points  are  cited :  The 
distribution  of  the  Negri  bodies  does  not  corre- 
spond with  the  greatest  concentration  of  the  virus 


HYDROPHOBIA.  511 

in  the  nervous  tissue,  the  latter  being  most  abun- 
dant in  the  medulla  and  pons  where  the  Negri 
bodies  are  encountered  rarely.  They  are  not  found 
invariably  in  animals  dying  of  hydrophobia.  They 
present  certain  analogies  with  "protoplasmic  in- 
clusions" seen  in  other  conditions,  as  in  carcinoma, 
variola,  etc.  Eemlinger  found  that  the  virus 
passes  through  appropriate  Berkefeld  filters,  and 
for  this  reason  Schlider  holds  that  the  bodies  of 
Negri,  being  too  large  for  filtration,  can  not  be 
considered  as  the  specific  organism.  The  view  of 
Schlider  may  be  criticized,  since  the  smallest 
Negri  bodies  are  so  minute  that  their  filtration 
would  seem  to  be  possible.  Nevertheless,  it  must 
remain  doubtful  Avhether  bodies  one  micron  in  di- 
ameter, the  proliferation  of  which  has  not  been 
proved,  may  be  considered  as  parasites.  The  hy- 
pothesis of  Negri  is  hardly  on  a  satisfactory  basis 
at  present.  Eemlinger  considers  the  bodies  as 
"involution  forms"  of  the  tissue  cells  which  have 
been  invaded  by  the  true  parasite. 

The  filterability  of  the  viriis  argues  for  its  mi-  Fiiterabinty 
croscopic  size.  By  means  of  filtration  one  may 
isolate  it  even  from  brains  which  are  badly  decom- 
posed, and  the  method  renders  it  possible  to  ob- 
tain pure  cultures  for  purposes  of  immunization. 
Inoculation  Avith  filtered  virus  is  sometimes  fol- 
lowed by  a  prolonged  incubation  period  which  may 
depend  on  the  retention  of  many  of  the  organisms 
by  the  filter.  A  similar  effect  was  produced  by 
Hogyes  by  inoculating  with  diluted  virus. 

By  prolonged  centrifugation  of  an  emulsion  of 
infected  nervous  tissue  the  overlying  fluid  loses  its 
infectiousness. 

The  possibility  that  the  organism  secretes  a  sol- 


of  Virus. 


512  INFECTION    AND    IMMUNITY. 

Toxin,  ublc  toxin  is  inii)ortant  from  the  stanilpoint  of  im- 
munization. A  number  of  observers,  particularly 
Babes,  and  Heller  and  Bertarelli,  noted  that  fil- 
trates of  infected  nervous  tissue  sometimes  cause 
emaciation,  paralyses  and  eventual  death  witiiout 
producing  a  disease  which  is  transmissible  to  other 
animals.  The  organism  is  without  doubt  toxic, 
but  these  results  give  us  no  idea  of  the  nature  of 
the  toxin. 
Resistance  The  virus  of  hydrophobia  as  contained  in  the 
central  nervous  system  of  infected  animals  exhib- 
its strong  resistance  to  chemical  germicides.  Five 
per  cent,  carbolic  acid  destroys  it  in  fifty  minutes, 
1  per  cent,  in  three  hours,  and  1-1000  corrosive 
sublimate  in  three  hours  (Marx).  It  resists  the 
action  of  putrefactive  bacteria,  and  has  been  found 
virulent  in  animals  which  had  been  buried  for  two 
to  four  weeks,  even  when  the  brain  was  putrid.  Di- 
rect sunlight  destroys  it,  however,  in  a  very  short 
time.  According  to  Tizzoni  and  Bongiovanni,  the 
rays  of  radium  have  a  destructive  action  on  the 
virus.  It  is  less  resistant  to  heat,  being  destroyed  in 
one-half  hour  at  a  temperature  of  52-58°  C. 
(Hog5'es),  but  is  not  affected  by  the  temperature 
of  liquid  air  for  three  months.  Chlorin  destroys 
it  very  rapidly.  It  is  gradually  weakened  by 
desiccation,  as  first  shown  by  Pasteur,  the  virus 
probably  undergoing  gradual  death  rather  than 
mere  attenuation.  It  is  said  to  be  attenuated  by 
the  action  of  the  gastric  juice  and  by  the  bile. 
When  the  nervous  tissue  is  emulsified  in  glycerin, 
virulence  is  retained  for  months  (Eoux).  On  the 
other  hand,  glycerin  appears  to  destroy  the  viru- 
lence of  filtrates  (Di  Vestea). 

Pasteur  gave   the  name  of  street  virus    {virus 


HYDROPHOBIA. 


513 


de  rue)  to  that  obtained  from  the  nervous  tissue  of  street 

_         -  ,         Virus  and 

dogs  m  which  the  disease  develops  spontaneously.  Fixed  virus. 
When  the  street  virus  is  injected  subdurally  into 
the  rabbit  the  latter  develops  hydrophobia  only 
after  an  incubation  period  of  from  two  to  three 
weeks.  If,  however,  this  virus  is  passed  from  one 
rabbit  to  another,  its  virulence  gradually  increases 
until  the  incubation  period  decreases  to  six  days. 

At  this  point  it  is  called  fixed  virus  {virus  fixe), 
and  its  virulence  can  not  be  further  increased. 
Passage  through  the  cat,  fox  and  wolf  also  in- 
creases virulence.  On  the  other  hand,  by  passing 
it  repeatedly  through  the  monkey  (Pasteur),  the 
chicken  (Kraus)  or  the  dog  it  becomes  attenuated 
for  the  rabbit  and  virulence  may  be  lost  entirely. 

Although  virus  fixe  represents  its  highest  degree  Low  virulence 

£      ■      T  £  m  -i.       XI  f  £         of  Fixed  Viru» 

ot  Virulence  lor  rabbits,  there  is  good  reason  lor  for  Man. 
believing  that  repeated  passage  through  the  rab- 
bit decreases  the  virulence  of  the  virus  for  man. 
In  other  words,  street  virus  is  more  infectious  for 
man  than  fixed  virus.  This  may  to  some  extent  ac- 
count for  the  success  of  the  Pasteur  treatment. 
Ferran,  indeed,  uses  unaltered  virus  fixe  for  the 
protective  inoculation  of  man. 

B}^  means  of  inoculation  experiments  the  virus  Distribution  of 
m.ay  be  demonstrated  invariably  in  the  brain,  Body.'" 
spinal  cord,  and  usually  in  the  salivary  glands  and 
saliva  of  animals  which  have  died  of  the  disease. 
These  tissues  are  specifically  affected,  and  the  virus 
probably  proliferates  in  thein.  By  one  or  another 
observer  its  presence  in  the  following  organs  and 
excretions  has  been  demonstrated :  Suprarenal 
gland,  lachrymal  gland,  vitreous  humor,  urine,  tes- 
ticular secretion,  lymph,  milk,  in  the  peripheral 
nerves  and  cerbrospinal  fluid.     Marx  states  that 


514  INFECTIOy    AXD    ntMUMTY. 

it  has  not  been  J'ouml  in  the  liver,  spleen,  blood  and 
aqueous  Ininioi-.  C'ounnont  and  Xicolas  found  it, 
however,  in  the  aqueous  liumor  of  rabbits  after 
death.  The  possibility  of  postmortem  invasion  of 
this  fluid  has  been  suggested.  It  has  been  found 
occasionally  in  human  saliva  during  life,  and  at 
the  site  of  the  wound  following  death  (Pace). 
Means  of  Hydroplioljia  is  transiiiilted  almost  exclusively 
by  the  bites  of  infected  animals,  the  virus  being 
conveyed  in  the  saliva.  Accidental  inoculation  may 
occur  in  handling  infected  tissues.  The  virus  does 
not  penetrate  the  intact  skin,  and  it  is  customary  to 
consider  a  bite  as  harmless  unless  the  continuity 
of  the  skin  is  broken.  Experimentally,  infection 
has  been  caused  by  placing  the  virus  on  the  mu- 
cous membranes  of  the  conjunctiva,  nose  and 
mouth,  in  the  absence  of  discernible  lesions.  Pace 
mentions  a  man  who  contracted  the  disease  after 
his  rabid  dog  had  inserted  the  tip  of  its  tongue  in 
his  (the  patient's)  nose.  But  one  authentic  ex- 
ample of  transmission  from  man  to  man  is  found 
in  medical  literature.  This  occurred  through  kiss- 
ing or  biting,  during  coitus.  In  rare  instances  it 
seems  to  have  been  transmitted  from  the  mother 
to  the  fetus  in  rabbits. 

The  dog  is  the  most  common  carrier  of  hydro- 
phobia. In  some  countries  (Russia, Hungary)  rabid 
wolves  cause  many  infections.  The  disease  has  been 
conveyed  by  the  bite  of  tlie  cat,  mouse  and  horse. 
and  possibly  by  the  skunk  in  some  of  our  western 
states.  The  dog  is.  however,  the  natural  host  of 
the  parasite,  and  either  by  his  bite  or  by  experi- 
mental inoculation  practically  all  animals,  at  least 
mammalians,  may  be  infected. 

The  incubation  period  in  animals  varies  from 


HYDROPHOBIA. 


515 


two  weeks  to  several  montlis.  In  man  it  varies 
between  twenty  and  sixty  days  usually,  but  may  be 
as  short. as  seven  or  ten  days,  or  as  long  as  twenty 
months  (rare).  In  children  it  is  shorter  than  in 
adults.  The  location  of  the  bite  is  also  of  impor- 
tance in  determining  the  length  of  incubation.  It 
is  shortest  following  wounds  of  the  head  and  neck, 
somewhat  longer  when  the  injury  is  in  the  hand  or 
arm,  and  still  longer  when  in  other  parts  of  the 
body.  The  degree  of  laceration  is  also  a  factor,  de- 
pending possibly  on  the  introduction  of  largei; 
quantities  of  virus,  and  on  larger  surfaces  for  its 
absorption.  The  bite  of  the  wolf  is  said  to  be  most 
virulent,  and  next  in  virulence  is  the  bite  of  the 
cat  and  dog. 

Not  all  who  are  bitten  by  rabid  animals  develop 
hydrophobia.  Correct  figures  on  this  point  are  dif- 
ficult to  obtain,  since  in  many  instances  the  ani- 
mals are  only  suspected  of  being  rabid.  According 
to  Hogyes,  15  to  16  per  cent,  of  those  who  are  bit- 
ten contract  hydrophobia.  The  percentage  is  much 
higher  following  bites  by  the  wolf.  The  disease  is 
invariably  fatal  to  man. 

The  symptoms  of  hydrophobia  in  man  differ  in 
no  essential  respects  from  those  seen  in  animals. 

The  immediate  determination  of  hydrophobia 
in  dogs  which  have  bitten  man  is  of  the  greatest 
importance.  In  many  instances  the  behavior  of  the 
animal  is  sufficiently  characteristic  to  justify  clin- 
ical diagnosis  of  the  disease.  The  disposition  of 
the  animal  changes  suddenly,  it  ceases  to  play,  eats 
various  indigestible  substances,  as  glass,  iron  and 
wood,  utters  pathognomonic  (?)  long-drawn-out 
howls,  may  become  ferocious,  or,  on  the  •  other 
hand,  quiet  and  sullen.     At  autopsy  the  meninges 


Incubation 
Period. 


Diagnosis 
in  Dogs. 


olti  l\J'j:rTI().\    AM)    IMMIMTY. 

and  iKTvous  tissue  are  congested  il'  tlie  disease  is 
advanced,  and  the  indigestible  mentioned  sub- 
stances may  be  found  in  the  stomach,  although  the 
latter  finding  has  little  or  no  diagnostic  importance. 
So-called       ^  number  of  histologic  changes  have  been  de- 

Spcciic 

Lesions,  scribcd  as  characteristic.  Among  these  are  the 
bodies  of  Negri,  described  above.  Remlinger  at- 
taches a  great  deal  of  importance  to  them  as  a 
means  of  diagnosis.  Babes  describes  perivascular 
nodules  of  lymphoid  cells  (Wutknotchen)  in  the 
medulla  and  cord.  The  lesion  of  Van  Geliuchten 
consists  of  a  proliferation  of  the  endothelial  cells 
(neuronophages)  surrounding  the  ganglionic  cells, 
the  latter  at  the  same  time  undergoing  atrophic 
and  degenerative  changes.  This  change  is  most 
marked  in  the  cervical  ganglia.  One  group  of  ob- 
servers finds  these  lesions  constant  in  animals 
■which  have  died  of  hydrophobia,  but  they  may  be 
absent  if  the  animal  is  killed  during  the  course  of 
the  disease;  hence  their  absence  does  not  exclude 
the  diagnosis  of  hydrophobia.  Others  have  found 
similar  changes  in  other  diseases.  Metchnikoff, 
it  will  be  remembered,  observed  the  destruction  of 
ganglionic  cells,  by  neuronophages  in  aged  dogs 
(page  179). 

We  are  hardly  able  at  present  to  consider  these 
changes  as  pathognomonic.  Particularly  in  early 
stages  of  the  disease  they  may  be  absent.  The  bite 
of  a  rabid  dog  is  infectious  in  from  two  to  four 
days  in  advance  of  the  development  of  symptoms, 
and  autopsy  performed  at  this  time  may  show 
neither  gross  nor  microscopic  changes  which  are 
characteristic.  In  communities  in  which  hydro- 
phobia is  known  to  be  endemic,  all  cases  of  dog  bite 
accompanied  by  penetration  of  the  skin  should  re- 
ceive the  Pasteur  treatment. 


HY  nun  I' no  HI  A. 


517 


A  great  deal  of  experimental  work  wliich  can  not  Eyiensipn 
be  given  in  detail  snows  conclusively  that  the  virus  Nerves. 
is  conveyed  to  the  central  nervous  system  by  means 
of  the  peripheral  nerves.  The  conditions  then  arc 
similar  to  those  in  tetanus  with  this  exception :  In 
hydrophobia  the  living  virus  reaches  the  central 
nervous  system^  whereas  in  tetanus  the  bacilli  re- 
main at  the  site  of  the  wound.  This  condition  ex- 
plains the  shorter  incubation  period  in  hydropho- 
bia, as  in  tetanus,  when  the  infection  atrium  is 
near  the  central  nervous  system  (e.  g.,  face).  When 
the  infection  is  introduced  into  any  particular 
part  of  the  body  surface,  the  virus  is  first  demon- 
strable in  the  corresponding  segment  of  the  cen- 
tral nervous  system.  Although  transmission  by 
the  nerves  is  the  rule,  infection  may  be  accom- 
plished in  rabbits  by  intravascular  injection.  On 
the  whole,  however,  infection  is  closely  associated 
with  the  wounding  of  nerves.  It  has  indeed 
been  shown  that  if  wounding  of  nerves  is. entirely 
avoided,  as  in  intraperitoneal  injections  into  rab- 
hits  (Marx)  the  full  virulent  nervou^s  tissue  may 
be  used  for  immunization.  A  single  injection  of  a 
large  quantity  brought  about  immunity  in  twelve 
days. 

The  muzzling  of  dogs  is  a  general  prophylactic  Prophylaxis. 
measure,  which  should  be  enforced  in  communities 
in  which  hydrophobia  is  known  to  occur.  No  mat- 
ter how  thoroughly  the  cauterization  and  antisep- 
tic treatment  of  wounds  is  carried  out  it  can  in  no 
case  be  depended  on  to  destroy  the  virus.  Even 
within  five  minutes  the  virus  may  be  carried  to  a 
point  which  is  beyond  the  reach  of  the  cautery.  In 
spite  of  this  fact,  however,  cauterization  should 
not  be  neglected,  even  when  the  Pasteur  treatment 


518 


IXFECTIOX    AM>    IMMiMTY. 


Preparation  of 
\irus  for  Pas- 
teur Treat- 
ment. 


Teclinic  of 
Treatment. 


can  be  instituted  at  once.  Tiie  greater  tlie  quantity 
of  virus  introduced  by  the  bite  the  shorter  will  be 
the  incubation  period,  and  there  is  good  reason  to 
believe  that  cauterization  (actual  cautery)  prop- 
erly carried  out  destroys  a  sufficient  amount  of 
virus  to  prolong  the  incubation  period.  A  long 
incubation  period  is  greatly  in  favor  of  the  success 
of  the  Pasteur  treatment. 

Pasteur's  first  protective  inoculations  were  car- 
ried out  with  virus  which  had  been  attenuated  by 
passage  through  the  monkey.  The  virus  fixe  ob- 
tained from  the  rabbit,  as  described  above,  was 
soon  substituted  for  that  of  the  monkey.  In  order 
that  an  antirabic  institute  may  continuously  have 
on  hand  a  sufficient  amount  of  vaccine,,  it  is  neces- 
sary to  inoculate  two  or  three  rabbits  daily.  For 
this  purpose  an  emulsion  of  the  medulla  of  a  rab- 
bit which  has  died  of  hydrophobia  is  inoculated  be- 
neath the  dura  mater.  A  short  time  before  the 
animals  would  die  of  the  disease,  they  are  killed 
by  bleeding,  and  the  spinal  cords  removed  with  all 
]')0ssiblc  precautions  for  asepsis.  Each  cord  is  cut 
into  two  parts  and  each  part  suspended  in  a  prop- 
erly constructed  jar  which  contains  solid  potas- 
sium hydrate.  After  the  jar  is  sealed  desiccation 
is  allowed  to  proceed  for  fourteen  days,  at  the  end 
of  which  time  the  infectiousness  of  the  tissue  has 
so  decreased  that  it  is  suitable  for  the  first  injec- 
tion.   The  vaccine  should  be  free  from  bacteria. 

As  is  well  Icno-wn,  the  Pasteur  prophylactic 
treatment  consists  of  the  subcutaneous  injection 
on  successive  days,  of  suitable  quantities  of  vims 
fixe,  prepared  as  described  above,  beginning  with 
the  cord  which  has  been  desiccated  for  fourteen 
davs  and  graduallv  usine:  fresher  cord?  until  viru- 


HYDROPHOBIA.  519 

lent  virus  lias  been  inoculated.  The  vaccine  is  jjre- 
pared  for  use  by  emulsifying  one  centimeter  of  a 
cord  in  5  c.c.  of  salt  solution  or  some  "artificial 
serum,"  and  in  a  single  treatment  from  1  to  3  c.c. 
of  this  emulsion  is  injected,  usually  into  the  sub- 
cutaneous tissue  of  the  anterior  abdominal  wall. 
In  this  region  there  is  less  likelihood  of  injuring 
large  nerves,  and  local  complications,  which,  how- 
ever, occur  rarely,  are  of  less  consequence. 

The  rapidity  with  which  one  should  pass  from 
the  fourteen-day  cord  to  fresh  virus  depends  on  the 
urgency  of  the  case.  When  there  is  good  reason  to 
suspect  a  short  incubation  period,  or  when  some 
days  have  followed  the  bite  an  "intensive"  treat- 
ment should  be  used ;  in  other  cases  the  progression 
may  be  slower.  The  following  conditions  augur 
a  short  incubation  period :  Bites  of  children,  who 
are  more  susceptible  than  adults,  and  in  whom 
the  injuries  usually  are  on  the  face;  bites  on  the 
face  and  neck  in  all  cases;  lacerated  wounds  in 
which  there  is  a  larger  surface  for  absorption  of 
the  virus.  The  influence  which  proper  cauteriza- 
tion exerts  on  the  incubation  period  was  mentioned 
above. 

The  table  on  page  520,  taken  from  Marx,  illus- 
trates a  "light"  and  an  "intensive"  treatment. 

This  scheme  is  variously  modified  in  different 
institutes,  especially  in  the  direction  of  a  more 
rapid  progression  to  virulent  material. 

Other  methods  of  attentuation  are  also  used,  as   of^er 

,1         o   Ti        •  TT      1  ■  1    •  p     p       ^  Means  of 

the  lollowmg:  Heating  emulsions  of  fresh  virus   Attenuation. 
at  58°  C.  for  different  lengths  of  time,  or  at  dif- 
ferent temperatures  (80°  to  30°  C.)  for  ten  min- 
utes (Babes-Puscari)  ;  digestion  of  virus  with  nat- 
ural or  artificial  gastric  juice   (Tizzoni  and  Cen- 


520 


INFECTION    AND    IMMUNITY. 


tanui)  ;  the  use  of  fresh  but  very  dilute  virus 
(Hi)gyes).  Ferran,  in  Barcelona,  inoculates  man 
with  the  fresh  unaltered  virus  fixe,  and  in  nearly 
3,000  cases  but  two  cases  of  hydrophobia  devel- 
oped. This  indicates  clearly  the  low  infectious- 
ness of  virus  fixe  for  man. 


Light. 

Intensive. 

Day  of 

Age  of 

Amount  of 

Day  of 

Age  of 

Amount  of 

Treat- 

Dried Cord 

Emulsion 

Treat- 

Dried Cord 

Emulsion 

ment. 

iu  Days. 

Injected. 

ment. 

iu  Days. 

Injected. 

1 

~v 

14 

3 

7^ 

3 

13 

3 

1 

J  13 

3 

*> 

j 

12 

3 

112 

3 

11 

3 

111 

3 

3 

10 

9 

3 
3 

2 

I? 

3 
3 

4 

• 

8 
7 

3 
3 

3 
3 

5 

. 

6 
6 

2 

2 

3 

\l 

2 

6 

5 

9 

i 

5 

2 

7 

") 

2 

5 

5 

2 

8 

4 

2 

6 

4 

2 

9 

3 

1 

7 

3 

1 

10 

5 

2 

8 

4 

2 

11 

5 

2 

9 

3 

1 

12 

4 

2 

10 

5 

2 

13 

4 

9 

11 

5 

2 

14 

3 

2 

12 

4 

9 

15 

3 

9 

13 

4 

2 

16 

5 

2 

14 

3 

9 

17 

4 

2 

15 

3 

2 

18 

3 

2 

16 

5 

2 

17 

4 

2 

18 

3 

9 

19 

5 

2 

20 

4 

2 

21 

3 

2 

It  seems  unnecessary  at  this  date  to  quote  sta- 
tistics to  show  the  value  of  the  Pasteur  treatment. 
Observations  indicate  that  immunity  is  not  fully 
established  until  about  fourteen  days  after  the 
completion  of  the  treatment,  and  in  a  certain  num- 
ber of  cases  the  disease  develops  before  this  time 
has  passed.  The  number  of  deaths  after  this  pe- 
riod is  exceedingly  small  and  has  grown  less  with 


HYDRO/'flO/ifA.  521 

improved  technic.  In  188G  the  number  of  deaths 
which  occurred  after  fifteen  days  had  passed 
amounted  to  0.94  per  cent.;  in  1902  to  0.18  per 
cent. 

The  immunity  established  by  the  Pasteur  treat-  immunity  and 
ment  is^  in  all  probability,  antimicrobic  in  nature,  enies. 
The  serum  of  both  man  and  animals,  after  immun- 
ization, is  able  to  destroy  the  infectiousness  of  rabic 
nervous  tissue,  i.  e.,  the  serum  is  rabicidal  (Babes 
and  Lepp,  1889).  The  technic  of  Kraus  and 
his  co-laborers  is  well  adapted  to  show  the  rabi- 
cidal properties  of  the  immune  serum.  Eabid  ner- 
vous tissue  is  made  into  an  emulsion  with  salt 
solution  in  a  dilution  of  1-100,  and  then  filtered 
through  paper  to  remove  coarse  particles  of  tissue. 
To  quantities  of  0.5  to  1.0  c.c.  of  this  emulsion 
varying  amounts  of  fresh  immune  serum  are  added, 
and  after  eighteen  hours'  contact  the  mixtures  are 
injected  into  rabbits  to  determine  the  degree  of 
infectiousness.  Small  quantities  of  rabicidal  sub- 
stance may  be  detected  in  this  way. 

Natural  resistance  to  hydrophobia  does  not  go 
hand  in  hand  with  the  antirabic  power  of  an  ani- 
mal's serum.  Old  pigeons,  for  example,  develop  the 
disease  following  intracerebral  injection  of  the 
vims,  although  their  serum  is  not  rabicidal. 

Babes  and  Lepp  also  showed  that  the  immune 
serum  has  protective  powers  which  are  analogous 
in  their  efficiency  with  those  of  bactericidal  serums. 
Babes  advocates  and  practices  the  mixed  method 
of  immunization  in  severe  cases,  immune  serum  be- 
ing injected  in  addition  to  the  virus.  The  serum 
has  little  or  no  curative  value. 


IM'KCTIO.S     AXD    IMMUNITY. 


II.   SYPHILIS. 


H>potheticai  It  is  iiiipossililo  ill  iliis  place  to  describe  or  even 
mention  tlie  niany  cocci,  bacteria  and  protozoa  (?) 
wliic-h  liave  been  brougbt  into  etiologic  relationship 
witli  syphilis.  Until  very  recent  times  the  bacil- 
lus of  Lustgarten  (Bacillus  syphilis  (?)  ),  occu- 
pied a  fairly  prominent  position  as  the  possible 
cause.  This  organism  resembles  the  tubercle  bacil- 
lus in  its  morphology  and  staining  properties,  and 
is  not  to  be  differentiated  from  one  of  the  smegma 
l)acilli.  Its  recognition  in  S5'philitic  lesions  has 
always  been  difficult,  and  by  far  the  greatest  num- 
ber of  investigators  have  been  unable  to  demon- 
strate it.  It  has  never  received  general  recognition 
as  the  cause  of  the  disease,  and  its  presence  in  le- 
sions of  the  genitals  has  no  significance  because  of 
the  occurrence  of  smegma  bacilli  in  this  locality. 

The  bacillus  of  De  Lisle  and  Julien,  and  that 

of  Joseph  and  Piorkowski  rest  on  no  better  basis. 

Two  important  discoveries  of  recent  date  lend 

to  the  hope  that  some  light  may  be  thrown  on  juany 

dark  problems  in  relation  to  syphilis. 

Transmission       The  first  has  to  do  with  the  transmission  of  the 

to  Monkeys. 

disease  to  lower  animals.  Such  attempts  have 
been  very  numerous,  both  by  the  inoculation  of 
syphilitic  tissues  and  of  organisms  cultivated  from 
the  tissues.  We  have  not  the  space  to  describe  in- 
dividual experiments,  and  can  only  say  that  trans- 
mission to  various  animals  (monkey,  guinea-pig, 
rabbit,  hog,  etc.)  has  been  claimed  in  a  number  of 
instances. 

Leaving  the  monkey  out  of  consideration,  it 
is  reasonably  certain  that  none  of  these  reported 
successes  represented  the  production  of  syphilis ; 
this  is  shown  decisively  by  experiments  published 


HYrJ/JLIS. 


523 


Metchnikoff 
and  Roux. 


by  Neisser  in  1902.  This  may  not  be  true,  how- 
ever, in  regard  to  the  inoculation  of  monkeys,  in 
which  successful  experiments  were  reported  by 
Ivlebs  (1879),  Martineau  and  Hamonic  (1882) 
and  Sperk  (1886-8).*  It  is  quite  likely  that  Sperk, 
in  particular,  accomplished  transmission  several 
times.  However,  the  successes  were  not  uniform, 
and  the  possibility  of  such  transmission  has  become 
an  assured  fact  only  in  the  most  recent  times. 

It  occurred  to  Metchnikoff  and  Eoux  as  it  had  Experiments  of 
occurred  to  others  that  the  monkey,  particularly 
the  higher  species  (chimpanzees),  should  on  ac- 
count of  their  biologic  proximity  to  man,  be  the 
most  suitable  animal  for  the  j)roduction  of  experi- 
mental syphilis.  Attention  has  already  been  called 
to  this  proximity  as  indicated  by  the  reaction  of 
serum  precipitins. 

Their  first  inoculation  was  performed  on  a  fe- 
male chimpanzee,  virus  from  a  primary  lesion  and  from"'Moni(ey 
from  mucous  patches  being  introduced  by  means 
of  scarification  into  the  prepuce  of  the  clitoris  and 
into  the  skin  of  the  eyebrow.  The  wounds  healed, 
and  twenty-six  days  after  inoculation  a  vesicle 
which  soon  was  surrounded  by  induration  appeared 
on  the  prepuce.  This  lesion  was  pronounced  a  typi- 
cal hard  chancre  by  eminent  dermatologists  and 
S3'philologists.  With  the  appearance  of  the  chan- 
cre the  inguinal  lymph  glands  became  enlarged 
and  one  month  later  a  papular  eruption  appeared 
on  the  thighs,  abdomen  and  back.  The  papules 
persisted  for  more  than  a  month,  and  were  still 
discernible  when  the  animal  died  several  weeks 
later  of  pneumococcus  infection.     Before  this  ani- 


Transmission 


*  Flexner  :  "The  Etiology  of  SyphUls."  Med.  News,  Dec.  9, 
1905. 


524  IM'LX'TION    AND    IMMUNITY. 

iiial  died  a  second  ehinipanzee  was  inoculated  from 
the  primary  and  secondary  lesions  of  the  first  ani- 
mal, resulting  in  the  development  of  primary  le- 
sions and  of  adenitis.  Still  another  successful  in- 
oculation resulted  in  secondary  lesions  with  the 
formation  of  mucous  plaques.  They  have  since 
performed  many  similar  experiments  with  positive 
results^  when  the  higher  types  of  monkeys  were 
used.  Confirmation  has  come  from  a  number  of 
independent  experimenters  (e.  g.,  Lassar,  A.  Neis- 
ser.  Kraus,  Flexner),  and  A.  Neisser  in  particular 
has  taken  up  the  work  on  an  extensive  scale. 
Experiments  Some  of  Neisscr's  work  is  of  the  utmost  impor- 
tance. The  experiments  of  Metchnikoff  and  Eoux 
had  already  indicated  that  the  higher  monkeys 
(chimpanzee,  etc.)  acquired  generalized  syphilis 
more  readily  than  the  lower  species.  Neisser's 
work  corroborates  this,  and  he  recognizes  a  scale  of 
susceptibility  which  corresponds  roughly  with  the 
proximity  of  the  different  species  to  man,  as  indi- 
cated by  general  morphology  and  the  reaction  of 
serum  precipitins.  The  chimpanzee,  orang-utan 
and  gorilla  are  the  most  susceptible,  and  the  syph- 
ilis produced  in  them  approaches  closely  that  seen 
in  man,  including  the  secondary  symptoms.  It  is 
suspected  that  the  cynocephalus  varieties  are  less, 
and  the  macacus  varieties  least  susceptible.  Among 
the  macaci  the  smaller  t3^pes  (rhesus)  are  more 
resistant  than  the  larger.  The  lower  susceptibility 
of  these  animals  is  recognized  by  the  failure  of 
secondary  symptoms  to  develop,  hence  in  them  the 
syphilis  may  be  purely  local  (Xeisscr).  The  study 
of  experimental  syphilis  is  so  young  that  generali- 
zations at  this  time  are  out  of  the  question. 
A  second  discovery  of  no  less  importance  was 


HYPIflLIH. 


525 


Possible  Cause. 


that  of  a  spirochetal''  {Spirocketa  pallida)  in  tho  Spirocheta 
primaiy  and  secondary  lesions'  of  syphilis  by  Hoff- 
mann and  Schaudinn  in  1905.  ''The  organism 
measures  from  4  to  10  microns  in  lengthy  the  aver- 
age being  about  that  of  the  erythrocyte  of  man. 
Its  width  varies  from  immeasurable  thinness  to 
one-half  micron.  It  possesses  from  three  to  twelve, 
sometimes  more,  curves,  which  are  sharp  and  reg- 
ular and  resemble  the  curves  of  a  corkscrew.  The 
poles  are  sharpened.  The  organism  is  mobile,  and 
the  motions  consist  of  rotations  on  the  long  axis, 
forward  and  backward  movements,  and  the  bend- 
ing of  the  entire  body.  Flagella  have  not  been 
seen''  (Flexner).  It  may  be  stained  by  the  azur 
of  Giemsa  or  the  Komanowsky  stain  or  some  one  of 
its  modifications.  Confirmation  has  come  from  a 
large  number  of  observers  in  rapid  succession, 
little  difficulty  being  found  in  demon^strating  the 
spirals  in  preparations  from  chancres  and  mucous 
plaques,  secondary  lesions  in  the  skiii  and  in 
fluid  aspirated  from  the  lymph  glands  which  are 
regional  to  the  chancre.  Schaudinn  found  it  once 
in  fluid  aspirated  from  the  spleen,  but  its  demon- 
stration in  the  blood  has  been  accomplished  in  only 
a  few  instances  after  prolonged  centrifugation  of 
the  blood.  Levaditi  and  Petresco  discovered  it 
in  the  fluid  of  an  artificially  produced  blister.  Two 
additional  facts  make  the  case  of  Spirocheta  pal- 
lida a  strong  one,  i.  e.,  its  occurrence  in  the  lesions 
of  the  congenitally  syphilitic  .and  in  the  experi- 
mental lesions  of  the  monke5\  even  when  the  inoc- 


Distribution 
of  Spirocheta. 


*  The  discovery  of  spirochetae  in  yaws,  by  Castellani  and 
by  Wellman,  is  a  very  suggestive  one,  in  view  of  tlie  tend- 
ency in  many  quarters  to  considers  yaws  as  a  manifestation 
of   syphilis. 


5-2ti 


IXFECTIOX    AM)    IMMIXITY. 


Illation  iti  made  from  a  previousl}'  infected  monkey 
(Kraus).  Iviiowledge  concerning  its  relation  to 
tertiary  lesions  is  not  yet  of  a  satisfactory  nature. 

Suggestive  as  these  results  are,  we  must  appre- 
ciate that  much  remains  to  be  learned  before  the 
causal  relationship  of  Spirocheta  pallida  to  syphilis 
can  be  an  unquestioned  one. 
Infection.  Infection  usually  is  venereal.  It  is  not  defi- 
nitely known  whether  a  defect  of  the  surface  of  the 
prepuce,  glans,  vagina,  etc.,  is  essential  for  infec- 
tion. The  epithelium  in  these  localities  is  so  deli- 
cate that  defects  of  microscopic  dimensions  may  be 
easily  produced,  and  infection  may  take  place 
through  such  defects  as  through  grosser  lesions.  It 
IS  well  known  that  the  lip,  tongue,  conjunctiva  and 
finger  may  be  the  seats  of  primary  lesions,  and  it 
is  probable  that  no  part  of  tlie  body  surface  is 
immune  when  the  virus  is  introduced  suitably. 

The  secretions  of  all  surface  lesions  in  syphilis 
are  infectious,  except  those  of  gummata.  Concern- 
ing the  infectiousness  of  different  normal  secre- 
tions and  the  situation  of  the  virus  in  internal  or- 
gan?, we  may  look  forward  to  more  positive  infor- 
mation than  we  have  had  hitherto.  Defibrinated 
blood  and  serum  from  cases  of  secondary  syphilis 
did  not  produce  lesions  when  injected  subcuta- 
neously  and  intraperitoneally  into  monkeys  (Neis- 
ser).  Neisser  had  previously  performed  experi- 
ments on  man  which  showed  the  serum  not  to  be 
infectious.  We  can  not  conclude  from  these  results, 
however,  that  the  blood  in  syphilis  is  not  infected. 
Inoculations  into  monkeys  from  the  internal  or- 
gans (liver,  spleen,  bone  marrow)  of  syphilitic 
monkeys,  gave  negative  results.  The  virus  is  non- 
filterable,  i.  e.,  it  is  so  large  or  its  form  is  such 
that  it  does  not  pass  through  a  Berkefeld  filter. 


Occurrence 
of  Virus. 


HYI'IULIH. 


527 


Clinical  e.\2)erience  indicates  that  the  virulence  virulence. 
of  the  syphilitic  virus  is  not  uniform.  It  is  pos- 
sible that  certain  strains  are  more  likely  to  bring 
about  "post-syphilitic"  diseases  than  others.  That 
the  resistance  of  the  virus  outside  the  body  is  low 
seems  evident  from  the  fact  that  transmission  is 
practically  unknown  except  as  it  occurs  by  direct 
contact.  Neisser  destroyed  it  by  heating  to  60°  C. 
for  thirty  minutes,  but  at  this  temperature  for  ten 
to  twenty  minutes  its  virulence  for  monkeys  was 
retained. 

Prophylaxis  demands  no  principles  not  generally 
known. 

Susceptibility  to  syphilis  varies  a  great  deal,  not 
in  the  sense  that  some  are  immune,  but  in  that  a 
more  virulent  type  of  disease  develops  in  some  than 
in  others.  This  is  a  condition,  however,  which 
is  difficult  to  differentiate  from  variations  in  the 
virulence  of  the  infecting  agent.  Syphilis  is  said 
to  be  particularly  virulent  when  introduced  into 
a  race  of  people  for  the  first  time. 

The  subject  of  immunity  to  syphilis  is  one  of  immunity. 
such  proportions,  the  phenomena  are  so  varied, 
and  knowledge  so  inaccurate,  that  a  thorough 
analysis  can  not  be  undertaken  in  this  place.  It 
is  the  customary  belief  that  one  attack  confers 
permanent  immunity  to  a  second.  To  what  ex- 
tent the  acquired  resistance  to  reinfection  signifies 
a  state  of  immunity  is  not  satisfactorily  settled. 
It  seems  well  established  that  within  a  relatively 
short  period  following  the  appearance  of  a  chancre 
a  second  primary  lesion  can  not  be  acquired.  It 
would  be  impossible  to  refer  this  resistance  to  ac- 
tual immunity  in  view  of  the  fact  that  the  indi- 
vidual is  at  the  moment  the  subject  of  systemic 
infection.     A  second  infection  would  be  but  a  su- 


528  INFECTION    AND    IMATUNITY. 

perimposed  infection   and  may  not  be  recogniz- 
able Avithout  tbe  formation  of  a  new  chancre.   The 
resistance  which    is    continued   into  the  tertiary 
stage,  at  a  time  when  the  individual  usually  has 
lost  infectiousness  for  others,  is  equally  obscure. 
If  the  present  hope  that  Spirocheta  pallida  will 
be  shown  to  be  the  cause  of  the  disease  is  realized, 
and  if  experimental  work  wdth  the  monkey  yields 
the  results  which  it  seems  to  promise,  those  and 
many  other  questions  of  fundamental  importance 
may  be  elucidated.     Among  such    questions  are: 
the  immunity  of  a  mother  who  gives  birth  to  a 
child  infected  by  the  father  at  the  time  of  concep- 
tion (Colle's  law) ;  the  occasional  occurrence  of  re- 
infection;  the  persistence   of   infectiousness   and 
transmission  of  the  disease  into  the  third  genera- 
tion, of  Avliich  there  are  a  number  of  reported  ex- 
amples. 
Serum        Scruiii-the'rapv,  or  vaccination  against  syphilis, 
are  possibilities  of  a  future  time.     A  truly  anti- 
syphilitic  serum  has  not  yet  been  demonstrated. 
Neisser  found  the  serum  of  syphilitics,  from  what- 
soever stage  of  the  disease,  without  influence  on 
the  course  of  the  infection.     Also  treatment  Avith 
the  normal  serums  of  various   insusceptible   ani- 
mals has  had  no  unqualified  success.    Metchnikoff 
and  Roux  observed  a  phenomenon  which  suggested 
to  them  the  possibility  of  attenuating  the  virus 
so  that  it  may  be  suitable  for  vaccination.    A  raa- 
cacus  monkey  reacted  to  inoculation  by  the  produc- 
tion of  a  local  lesion,  the  virus  of  which  when 
transferred    to    the  more  susceptible  chimpanzee 
likewise  caused  a  local  lesion,  but  no  signs  of  gen- 
eralization appeared.  The  chimpanzee  later  showed 
himself  resistant  to  the  virus  from  man,  and  for 


Therapy 


YELLOW   FEVEIi.  529 

this  reason  it  was  assumed  that  immunization  had 
been  accomplished.  Neisser  reasonably  criticises 
this  conclusion  on  the  ground  that  the  chimpanzee, 
having  been  inoculated,  with  syphilis  from  the 
monkey,  resisted  inoculation  from  man,  not  be- 
■  cause  he  was  immunized,  but  because  he  was  syphi- 
lized,  i.  e.,  he  was  already  infected  with  syphilis. 

III.    YELLOW  EEVER. 

Yellow  fever  is  peculiarly  an  American  disease,  occurrence. 
and  it  has  reached  other  continents  (e.  g.,  Spain) 
only  in  accidental  ways  and  for  brief  periods.  It 
is  possibly  endemic  in  certain  portions  of  West 
Africa  (Sierra  Leone),  to  which  it, was  probably 
carried  from  the  Antilles  (Scheube).  Scheube 
regards  the  Antilles  as  the  birthplace  of  yellow 
fever."  Knowledge  of  it  extends  only  to  the  middle 
of  the  seventeenth  century,  at  which  time  it 
surely  existed  in  the  West  Indies.  The  dis- 
ease has  on  several  occasions  been  carried  to 
Spain  by  vessels  returning  from  Cuban  ports. 
Until  very  recent  times  it  was  endemic  in 
Cuba,  especially  Havana,  and  in  Vera  Cruz 
and  other  Spanish-American  ports  it  has  prevailed 
extensively.  From  such  points  extension  frequent- 
ly takes  place  into  adjacent  tropical  or  subtropical 
regions,  or  even  into  temperate  localities  during 
the  summer  months.  In  the  latter  part  of  the 
eighteenth  century  Philadelphia  suffered  very  se- 
verely. Baltimore  was  attacked  similarly  and  Bos- 
ton to  a  less  degree.  Other  northern  ports,  e.  g., 
New  York,  have  experienced  attacks  of  limited 
duration,  the  disease,  presumably,  being  intro- 
duced by  means  of  infected  ships. 

In  addition  to  our  southern  coasts  and  that  of 
Mexico,  the  Atlantic  coast  of  South  America  has 


530 


IXFECTIOX    AM)    IMMLMTY. 


Bacillus 
Icteroides. 


The  Mosquito 
Theory. 


lu'on  infce-tcHl  as  far  south  as  Buenos  Ayres.  and 
likewise  the  western  coast  of  Mexico  and  Peiii.  In 
the  eighteenth  century  the  coast  of  Spain  and 
Portugal  suflFerod  severely,  but  since  that  time 
only  minor  epidemics  have  occurred  in  these  coun- 
tries. Epidemics  frequently  have  appeared  on 
ships  after  they  had  left  infected  ports. 

The  Southern  States  were  invaded  repeatedly  in 
the  last  decade  of  the  eighteenth  century,  in  1803, 
1805,  1853,  18G7,  1873,  1878,  1905,  and  in  lesser 
degrees  at  other  times,  in  all  ninety-six  times.  The 
severest  epidemics  w^ere  those  of  1853  and  1878. 

The  many  microbes  which  have  been  cited  as  the 
cause  of  yellow  fever  need  not  be  described.  The 
BaciUus  icteroides  of  Sanarelli,  which  had  at- 
tained more  prominence  than  any  other,  was  shown 
by  Sternberg,  by  Reed  and  Carroll  and  by  the  more 
recent  work  on  the  mosquito  theory,  to  bear  no 
causal  relationship  to  the  disease.  According  to 
Eeed  and  Carroll  it  is  identical  witli  the  hog-chol- 
era bacillus. 

The  monumental  work  of  Reed,  Carroll,  Agra- 
monte  and  Lazear  (1900),  the  last  of  whom  lost 
his  life  from  yellow  fever,  has  made  it  possible 
to  replace  accurate  knowledge  of  the  epidemiology 
and  prophylaxis  of  yellow  fever  and,  to  a  certain 
extent,  of  its  etiology,  for  many  incorrect  ideas 
which  had  prevailed  up  to  that  time. 

The  conception  that  yellow  fever  is  transferred 
from  one  person  to  another  by  moscpiitoes  was 
first  advanced  positively  by  Carlos  Finlay,  a 
Cuban  physician,  in  1881,  although  several  Ameri- 
can physicians  had  long  before  noted  the  preva- 
lence of  mosquitoes  during  yellow  fever  outbreaks 
(Rush,    1793;    Weightman,^  1839;    Wood,    1853; 


YELLOW   FMVMR.  531 

Barton,  1853).  He  reported  tlie  trariHnnssJon  of 
the  disease,  experiinentally,  by  the  bites  of  inos- 
quitoes  which  liad  fed  on  yellow  fever  patients, 
and  stated  that  light  attacks  which  followed  the 
bites  resulted  in  the  establishment  of  immunity. 
The  subsequent  observations  of  Eeed  and  his  co- 
workers indicate,  however,  that  Finlay's  technic 
was  such  that  he  could  not  possibly  have  produced 
experimental  fever,  and  that  the  development  of 
the  disease  in  his  subjects  was  purely  a  coincidence. 
The  reason  for  this  will  appear  below. 

Having  satisfied  themselves  that  Bacillus  icte-  The  work  of 
roides   is   but   an   accidental   organism   in   yellow   Etc., with stego- 

n  1    J.^      L    -1.    •      J!  -\  1  ^  T       myia    Fasciata. 

fever,  and  that  it  is  found  under  normal  condi- 
tions as  well,  Eeed  and  his  associates  began  work 
on  the-  mosquito  hypothesis  of  Finlay.  The  first 
positive  result  was  obtained  in  the  case  of  Dr.  Car- 
roll. Carroll  "was  bitten  at  2  p.  m.,  Aug.  27,  1900, 
by  Btegomyia  fasciata.  This  particular  mosquito 
had  •  bitten  a  severe  case  of  yellow  fever  on  the 
second  day  of  the  disease,  twelve  days  before;  a 
mild  case  of  yellow  fever  on  the  first  day  of  the 
attack,  six  days  preceding;  a  severe  case  of  yellow- 
fever  on  the  second  day  of  the  attack,  four  days 
before;  a  mild  case  of  yellow  fever  on  the  second 
day  of  attack,  two  days  before  inoculation."  After 
an  incubation  period  of  three  days,  Carroll  devel- 
oped typical  and  severe  yellow  fever,  from  which 
he  recovered.  A  similar  result  in  one  other  case 
was  reported  at  this  time,  and  later  Camp  Lazear, 
with  mosquito-proof  houses,  was  established  for  the 
continuation  of  the  study.  The  experiments  of 
Eeed  and  his  co-workers,  and  confirmatory  work  by 
Guiteras  and  the  French  commission,  can  not  be 
described  in  this  place.     We  ma}^  feel  sure,  how- 


532  IXFECTION    AXD    IMMUNITY. 

Important  Facts  evGi",  that  witli  all  tliG  conditioiis  of  experiineuta- 

Been  Learned,    tioil    lindcr    absolutC    COntlol    thc    followillg    poillts ' 

have  been  determined  with  scientific  certainty:  1. 
Yellow  fever  may  be  transferred  from  a  patient  to 
a  non-immune  by  the  bite  of  a  mosquito — Stego- 
inijia  fasciala — which  has  previously  fed  on  the 
yellow  fever  patient.  3.  In  order  that  the  mos- 
quito become  infected  it  is  necessary  for  him  to 
feed  on  yellow  fever  blood  within  the  first  few 
days  (three  days)  of  the  fever.  3.  The  mosquito 
can  not  transfer  yellow  fever  directly  and  imme- 
diately from  the  patient  to  a  non-immune,  but  it 
is  necessary  for  a  period  of  not  less  than  twelve 
days  to  elapse  before  he  becomes  infectious.  When 
this  time  has  been  reached  the  insect  continues  in- 
fectious for  at  least  fifty-seven  days  and  probably 
throughout  his  life.  4.  Yellow  fever  can  not  be 
transferred  by  "fomites.'^  5.  The  subcutaneous  in- 
jection of  yellow  fever  blood  into  a  non-immune 
produces  yellow  fever,  hence  the  infecting  agent 
exists  in  the  circulation.  6.  The  serum  of  a  yel- 
low fever  patient,  after  being  diluted  and  filtered 
through  a  Bcrkefeld  filter  (Eeed  and  Carroll)  or 
Chamberland  B  porcelain  filter  (Eosenau,  Parker, 
Francis  and  Beyer)  is  infectious,  hence  the  in- 
fecting agent  at  some  stage  of  its  development  is 
very  minute,  possibly  ultramicroscopic.  7.  "An 
attack  of  yellow  fever  produced  by  the  bite  of  a 
mosquito  confers  immunity  against  the  subsequent 
injection  of  the  blood  of  an  individual  suffering 
from  the  nOn-experimental  form  of  this  disease" 
(Eeed,  Carroll  and  Agramonte).  8.  The  period  of 
incubation  usually  is  three  days,  but  may  vary 
within  the  limits  of  two  to  six  days.  9.  "A  house 
may  be  said  to  be  infected  with  yellow  fever  only 


and  Stegomyia. 


YJ^JLLOW   FEVER.         '  533 

Avhen  there  are  present  within  its  walls  contami- 
nated mosquitoes  capable  of  conveying  the  parasite 
of  the  disease."  10.  "The  spread  of  yellow  fever 
can  be  most  effectually  controlled  by  measures 
directed  to  the  destruction  of  mosquitoes  and  the 
protection  of  the  sick  against  the  bites  of  these 
insects."  11.  No  mosquito  other  than  Stugomyia 
fasciata  has  been  found  capable  of  transmitting 
the  disease,  and  analogies  suggest  the  probability 
that  no  other  insect  is  concerned. 

These  discoveries  explain  many  facts  in  rela-  Epidemiology 
tion  to  yellow  fever  which  had  been  obscure  hither- 
to. For  example,  yellow  fever  is  a  tropical  and 
subtropical  disease  only  because  Stegomyia  fas- 
ciata breeds  in  tropical  and  subtropical  climates. 
The  disease  is  found  in  low,  moist  localities  rather 
than  in  the  high  and  dry,  because  the  mosquito  in- 
habits the  former  and  not  the  latter.  Yellow 
fever  dies  out  with  the  first  severe  frost  or  on  the 
advent  of  cool  weather  because  these  conditions 
either  kill  the  mosquito  or  cause  him  to  hibernate. 
The  advent  of  an  initial  case  of  yellow  fever  in  a 
suitable  region  is  followed  by  the  appearance  of  the 
disease  in  epidemic  form  only  after  a  period  of  two 
or  three  weeks,  because  the  mosquito  first  becomes 
infectious  in  about  two  weeks  after  it  has  fed  on 
yellow  fever  blood;  this  may  correspond  with  a 
certain  stage  of  development  of  the  as  yet  unrecog- 
nized parasite.  The  observation  often  made  that 
yellow  fever,  like  malaria,  is  not  contagious  in  the 
ordinary  sense,  in  spite  of  its  rapid  extension,  is 
readily  understood,  as  is  the  irregular  method  in 
Avihch  the  disease  spreads.  It  is  now  clear  why  the 
disinfection  of  fomites  has  never  been  able  to 
check  the  advance  of  an  epidemic,  and  why  the 


■>:!4  i\j'j:cti().\     \\I)   nnii  mty. 

ordinary  quarantine  measures  wliieh  (.lid  not  take 
tlie  mosquito  into  consideration  were  not  eU'oetive 
in  keeiiinu'  tlie  disease  out  of  a  ra\()i-able  port;  and 
lu'  ii  J'avorahle  port  is  meant  one  which  can  harhor 
Stegonii/ia  fasciata.  These  discoveries  also  c.\- 
})lain  liow  yellow  fever  could  be"  stamped  out  oi" 
Havana^  Texas  and  Xcw  Orleans  by  i)rophylactic, 
hygienic  and  quarantine  measures,  which  had  as 
their  objects  tlie  destruction  of  the  mosquito  and 
its  breeding  places  and  prevention  of  the  infection 
of  the  mosquitoes  l)y  suitably  screening  the  pa- 
tients. 
Distribution  of  ]t  is  thus  sccn  that  the  epidemic  occurrence  of 
yellow  fever  is  strictly- associated  witli  the  distribu- 
tion of  Stegomyia  fasciata.  Howard,  in  Bulletin 
Xo.  46  of  the  Public  Health  Eeports.  gives  this 
distribution  as  known  on  Sept.  l<t.  lOO.").  and  pub- 
lishes a  map  showing  the  region  which  the  insect 
may  be  expected  to  inhal)it. 

Stegomyia  fasciata  has  been  found  in  the  following 
localities  in  the  United  States   (Howard)  : 

Virginia:  Virginia  Beach,  Xorfolk,  Lj-nchburg,  Dan- 
ville, Richmond.  Kentucky:  Lexington,  Middlesboro, 
Louisville,  Richmond.  Illinois:  Cairo.  Tennessee : 
Nashville,  Knoxville,  Clarksville,  Chattanooga,  Memphis, 
Columbia,  Decherd,  Athens,  Bristol.  Arkansas:  Hot 
Springs,  Helena.  Louisiana:  Ruddock.  New  Orleans. 
Baton  Rouge.  Napoleonville,  Covington,  Hammond, 
Shreveport.  Franklin,  ]\Iorgan  City,  New  Iberia,  Patter- 
son. Mississijypi :  Pass  Christian,  Summit,  Quarantine 
Station,  Vicksburg,  Clarksdale,  Tutwiler,  Belzoni,  Holly 
Springs,  Jackson,  Wonona,  West  Point,  Tupelo,  Corinth, 
Agricultural  College,  Biloxi.  Alabama:  Mobile,  Decatur, 
Aubiu'n,  Tuscumbia,  Huntsville,  Yazoo  City.  Georgia: 
Atlanta.  Pelham,  Augusta,  Savannah,  Brunswick. 
Florida:  Barrancas.  Key  West.  Texas:  Galveston, 
Houston,  Victoria,  San  Diego,  Tyler,  Laredo,  Austin. 
San  Antonio,  Corsicana.  Brownsville.  Alice,  Colorado, 
Dallas,  Paris,  Edna.  Fort   Bliss    (El  Paso),   Fort  Ring- 


YELLOW   FKVEIi.  r>:i-> 

gold  (Rio  Urando-Ludlow).  Houth  Carolina:  Charles- 
ton, Columbia,  Fort  Freniont,  Sullivan's  Island.  Ari- 
mona:  Nogales.  Maryland:  Baltimore  (Carter) — breed- 
ing in  fresh  water'on  fruit  wharf.  North  Carolina:  Beau- 
fort, Winston,  Raleigh,  Greensboro,  Charlotte,  Salisbury. 
Indiana:    Jefl'ersoftville.    Missouri:    St.  Louis. 

Eeed  and  Carroll  found  the  larvffi  of  stegomyia  Breeding  Places 

"(1)  in  rain-water  barrels;  (2)  in  tin  cans  that 
had  been  used  for  removing  excreta  and  which 
still  contained  a  small  amount  of  fecal  matter; 
(3)  in  sagging  gutters  containing  rain  water; 
(•f)  in  cesspools;  (5)  in  tin  cans  placed  about 
table  legs  to  prevent  the  inroads  of  red  ants;  (6) 
in  the  collection  of  water  at  the  base  of  the  leaves 
of  the  agave  americana;  (7)  in  one  end  of  a 
horse  trough  that  was  in  daily  use."  These  in- 
stances are  cited  to  show  the  general  character  of 
the  places  in  which  the  eggs  and  larvae  of  stegomyia 
may  be  found.  The  eggs  are  deposited  during  the 
night,  in  about  seven  days  after  the  ingestion  of 
blood,  and  "in  pairs,  in  groups  of  three  or  more 
or  singly,"  to  the  number  of  forty-seven  on  the 
average  (Eeed  and  Carroll).  The  eggs  are  very 
resistant  to  drying  and  extreme  cold  ( — 17°  C). 
With  a  favorable  temperature  they  hatch  in  from 
three  to  seven  days ;  the  larval  stage  lasts  for  seven 
days,  the  pupal  two  days,  the  total  cycle  being 
completed  in  about  twelve  days.  As  in  the  case  of 
anopheles,  only  the  female  stegomyia  sucks  blood. 
The  insect  prefers  the  hours  from  3  p.  m.  to  9  a. 
m.  for  feeding,  but  is  most  active  from  4  p.  m. 
to  midnight.  "In  captivity  the  hungry  impreg- 
nated female  will  bite  at  any  hour  of  the  day  or 
night."  In  a  state  of  freedom  it  will  not  bite  a 
second  time  for  from  five  to  seven  days.  It  ap- 
pears not  to  bite  when  the  temperature  is  lower 


536  IM'ECnOX    AM)    IMMLMTy.. 

Time  of  tliau  6"i°  F.,  auotliei  factor  in  the  subsidence 
'  '"*'■  of  yellow  fever  with  the  advent  of  cool  weather. 
For  further  details  concerning  the  morphology, 
biology  and  habits  of  stegomyia  consult  Howard 
on  "The  lilosquito" ;  Eeed  and  Carroll,  "The  Pre- 
vention of  Yellow  Fever,"  Medical  Record,  Oct. 
26.  1901;  Parker.  Beyer  and  Pothier,  "Eeport 
of  Working  Party  No.  1,"  Yellow  Fever  Institute 
Bulletin  Xo.  13,  1903,  Washington. 

Importation  YcUow  fcvcr  cascs  and  stegomyia  work  together 
"**'  in  the  extension  of  the  disease  just  as  malarial 
.  cases  and  anopheles  do  in  the  extension  of  ma- 
laria; for  the  principles  involved  the  chapter  on 
malaria  may  be  consulted.  Of  particular  interest 
is  the  importation  of  the  disease  by  means  of  ships, 
since  the  invasion  of  the  United  States  usually 
comes  about  in  this  way.  It  is  frequently  stated 
that  ships  lying  one-half  mile  from  shore  are  safe 
from  yellow  fever;  Grubbs,  however,  believes  that 
stegomyia  may  reach  vessels  lying  within  fifteen 
miles  of  the  shore  if  the  wind  is  favorable.  The 
insect  readily  boards  a  vessel  lying  in  an  infected 
port  and  may  remain  there  at  least  during  a  sev- 
enteen days'  voyage.  It  may  also  breed  in  suitable 
barrels  or  tanks  of  water  on  the  ship.  Under  these 
conditions  it  is  readily  imderstood  how  a  ship, 
leaving  a  harbor  with  a  healthy  crew,  may  be  at- 
tacked by  yellow  fever  a  few  days  after  leaving 
port;  and  how  any  quarantine  measure  at  a  new 
port  which  does  not  involve  the  destruction  of  the 
mosquitoes  on  the  boat  and  the  protection  of  the 
patients  from  the  bites  of  mosquitoes  is  inadequate. 

Resistance  As  statcd,  the  nature  of  the  virus  is  unknown. 
Its  filterability  was  mentioned.  A  temperature 
of    55°    C.    for    ten     uiiinitos    renders   innocuous 


YELLO  W  FE  VER. 


537 


the  defibrinated  blood  of  tlic  infected;  according  to 
the  French  Commission  (Marchoux,  Salimbeni 
and  Simond)  the  virus  is  destroyed  in  five  minutes 
at  this  temperature.  Tlie  latter  also  found  that 
defibrinated  blood  when  sealed  under  vaselin  re- 
tained its  virulence  for  five,  but  not  for  eight  days. 
The  toxic  substance  appears  to  have  a  strong  af- 
finity for  the  parenchymatous  organs,  particularly 
the  liver  and  kidney. 

The  essential  jorinciples  of  prophylaxis  have  Prophylaxis. 
been  alluded  to :  1,  the  destruction  of  breeding 
places  for  the  mosquito  as  described  in  the  section 
on  malaria;  2,  the  isolation  of  patients,  screened, 
to  exclude  mosquitoes;  3,  the  destruction  of  mos- 
quitoes found  in  infected  houses  or  ships;  4,  the 
individual  factor  of  avoiding  the  bites  of  mos- 
quitoes, which  involves  the  screening  of  houses, 
and  individual  care.  One  may  go  about  more 
safely  in  the  middle  of  the  day  than  before  9  a. 
m.  and  after  3  p.  m.  For  the  disinfection  of 
Jiouses,  i.  e.,  for  the  destruction  of  mosquitoes,  two 
pounds  of  tobacco  or  two  pounds  of  pyrethrum 
powder  per  1,000  cubic  feet  of  space  may  be  burned 
after  the  rooms  are  sealed.  When  smaller  quan- 
tities are  used  the  insects. may  be  only  stupified, 
and  should  be  collected  and  burned  (Eosenau,  Par- 
ker, Beyer  and  Pothier) .  Sulphur  dioxid  is  highly 
efficient,  but  formaldehyd  is  valueless  as  an  in- 
secticide (Rosenau). 

The  negro  is  less  susceptible  to  yellow  fever  than  Susceptibility. 
the  white  man  and  in  him  the  mortality  is  lower. 
Among  the  natives  the  mortality  is  from  7  to  10 
per  cent.,  among  the  whites  from  20  to  80  per  cent. 
(Scheube).  The  statement  that  Caucasians  may 
become  "acclimated"  so  that  they  are  less  suscep- 


Immunitv  and 
Serum  Prop 


ry,is  i.\j'K("no.\    amj   lumlmty. 

tiblc  needs  additional  investigation.  Tt  seems  im- 
])ossil)le  that  aoeliinatization  eouM  iiiran  anytliing 
else  than  aetive  iininunizatimi.  CliiUlren  and  the 
aged  are  attacked  less  i'reqiuiilly  than  those  be- 
tween the  ages  of  ten  and  thirty. 

An  attack  of  yellow  fever,  whether  experimental 
erties.  or  natural,  confers  immunity  of  long  or  lasting  du- 
ration. According  to  the  French  Commission,  a 
certain  degree  of  immunity  could  he  conferred  In" 
the  injection  of  infected  serum  wliich  liad  hwn 
heated  to  55°  C.  for  five  minutes,  or  ol'  delll)i-i- 
nated  blood  Avhich  had  been  kept  under  vaselin 
oil  at  room  temperature  for  eight  days.  They  also 
claimed  that  the  serum  of  convalescents  has  pro- 
phylactic and  curative  properties  to  a  certain  de- 
gree.     • 

IV.    TYPHUS  FEVER. 

In  addition  to  a  streptobacillus  obtained  by 
Hlawa  and  the  diplococci  described  by  a  number 
of  investigators,  a  supposed,  protozoon,  resembling 
pyroplasma,  was  found  in  six  cases  by  Gotschlich. 
The  etiologic  role  of  none  of  these  organisms  can 
be  accepted  at  the  present  time. 
ocxurrence       Tvphus  is  uow  a  tare  disease.    It  is  endemic  on 

and  Conta-  •  J^  t  r^^  i    t  • 

giousness.  a  Small  scalc  m  London,  Glasgow  and  Ijiverpool, 
and  cases  occur  in  the  larger  cities  of  Ireland.  In 
epidemic  form  it  attacks  localities  in  which  the 
hygienic  conditions  are  bad.  The  contagion  seems 
to  fasten  itself  in  such  localities  and  does  not  ex- 
tend with  rapidity  to  neighboring  communities  in 
which  good  hygiene  and  cleanliness  prevail ;  it  is 
particularly  a  disease  of  the  poor,  the  filthy  and 
the  underfed.  Healthy,  clean  and  well-nour- 
ished persons  who  enter  an  infected  district  and 
come  in  contact  witli  tlie  patients  arc  subject  to 


TYPHUS.  FKVEIt.  539 

attack.  'I'yplius  has  always  been  considered  a  very 
contagious  disease.  It  has  been  noted  repeatedly, 
however,  that  when  patients  are  removed  to  a  hos- 
pital and  kept  under  clean  and  hygienic  conditions 
with  plenty  of  fresh  air  that  infection  of  attend- 
ants and  physicians  is  relatively  infrequent.  From 
observation  of  600  hospital  cases  Eobinson  and 
Potts  draw  particular  attention  to -this  point  and 
lay  great  stress  on  the  importance  of  liberal  ven- 
tilation in  decreasing  contagiousness.  The  method 
of  transmission  is  not  known.  It  has  been  sug- 
gested repeatedly  that  the  disease  may  be  spread 
by  the  bites  of  insects,  perhaps  fleas  and  bed-bugs. 
Gotschlich  emphasizes  the  latter  as  possible  car- 
riers, discrediting  the  significance  of  the  flea.  He 
notes  that  in  Alexandria  fleas  are  everywhere, 
whereas  typhus  is  confined  largely  to  the  poorer 
and  unclean  localities.  Transmission  by  means  of 
clothing  and  other  fomites  is  said  to  occur.  Usual- 
ly the  development  of  typhus  in  a  hitherto  unin- 
fected community  is  traceable  to  the  importation 
of  the  disease;  in  some  instances,  however,  the 
origin  could  not  be  learned. 

Proph3daxis  demands  the  isolation  and  disinfec- 
tion usually  practiced  in  combating  contagious 
diseases,  particular  attention  being  paid  to  hj^giene, 
cleanliness,  the  admission  of  fresh  air  to  the  sick 
room,  and  the  destruction  of  vermin  ( !). 

The  serum  of  convalescents  is  said  to  be  cura- 
tive in  a  moderate  degree  (Legrain). 

V.    DENGUE   FEVEE. 

Dengue  occurs  in  numerous  countries  which  af-  occurrence. 
ford  a  warm  climate.     It  is  endemic  in  Egypt, 
Arabia,    Senegambia,    Honduras,    the    Bermudas, 


540 


I.XFJ-JCTWX    AM)    IMMUNITY 


and  the  Sandwich  Jshuuls.  Important  centers  for 
the  origin  of  epidemics  are  the  lesser  Antilles  of 
the  Western  Hemisphere,  the  Red  Sea  Coast, 
and  Senegambia  (de  Brun,  cited  by  Scheiibe).  It 
occurs  in  our  southern  states  and  In  Mexico.  It 
may  be  introduced  into  new  regions  by  means  of 
infected  ships. 
Organisms.  The  specific  agent  is  unknown.  The  "plasmeba" 
described  by  Eberle  (190-i)  and  his  hypothesis  that 
Cidex  fatigans  may  transmit  the  disease  await  con- 
firmation. The  same  may  be  said  of  an  influenza- 
like organism  seen  by  Carpenter  and  Sutton 
(1905)  in  stained  preparations  from  the  throat. 

"Dengue  fever  is  an  acute  infectious  disease, 
distinguished  by  the  appearance  of  an  initial  and 
terminal  polj^morphous  eruption  and  accompanied 
by  severe  articular  and  muscular  pains."  Corre- 
sponding with  the  two  eruptions,  there  are  charac- 
teristically two  periods  of  temperature  separated 
by  a  short  period  of  apyrexia.  The  intense  muscu- 
lar pains  and  asthenia  resemble  those  of  influenza, 
the  respiratory  affections  of  the  latter  being  absent, 
however.  The  incubation  period  varies  from  a  few 
hours  to  four  or  five  days,  usually  one  or  two,  and 
the  entire  duration  from  six  to  seven  days. 
Transmission.  Dcngue  fever  extends  epidemically  with  all  the 
rapidity  which  characterizes  influenza.  "In  some 
respects  the  spread  of  the  disease  suggests  some 
peculiarity  in  the  method  of  propagation  differing 
from  that  of  the  well-known  diseases,  influenza, 
scarlet  fever,  measles,  etc.  It  appeared  to  spread 
particularly  to  contiguous  houses,  whole  streets 
Ijcing  attacked  seriatim.^^*     Dengue  prevails  espe- 


*  "Iteport  on  the  Dengue  Epidemic  in  Brisbane  in  100.5." 
rommittee  of  Queensland  Brancli  of  the  British  Medical 
Association.      .Tournal  of  Tropical   Medicine,  Dec.   1.5.    1005. 


DENGUE    FEVER.  541 

cially  during  the  hot  months.  "A  great  fall  of 
temperature  and  the  appearance  of  absolutely  cold 
weather  always  puts  an  end  to  the  epidemics" 
(Hirsch;,  cited  by  Scheube). 

The  disease  extends  so  rapidly,  and  the  incuba- 
tion period  is  so  short,  that  general  measures  of 
prophylaxis  would  seem  to  be  of  no  avail. 

Susceptibility  is  general,  even  in  infancy  and 
old  age.  The  disease  has  a  very  low  mortality; 
it  is  more  severe  in  very  early  and  very  late  life. 
Eelapses  are  not  infrequent,  and  one  attack  does 
not  confer  immunity.  Second  attacks  may  occur 
during  the  same  year.  Leucopenia  is  present  from 
the  first  (Carpenter  and  Sutton). 

VI.    ACUTE   ARTICULAR   RHEUMATISM. 

(See  pp.  359,  360.) 

VII.     SMALLPOX    AND    VACCINIA. 

Vaccinia  and  smallpox  may  be  considered  to-  Relation  of 
gether,  having  in  mind  the  likelihood  or,  indeed,  smai'ipox!" 
the  certainty,  that  they  have  a  common  etiology. 
This  view  seems  the  only  possible  one,  in  spite  of 
our  uncertainty  as  to  the  exact  nature  of  the  cause. 
To  hold  a  different  view  would  be  to  aclcnowledge 
that  immunization  with  one  kind  of  microbe  may 
confer  immunity  of  the  strongest  and  most  spe- 
cific character  against  another,  a  condition  for 
which  we  could  find  no  parallel. 

More  satisfactory  knowledge,  however,  comes  inocuiati«n  of 
from  actual  conversion  of  smallpox  virus  into  vac-  Infanltox!***' 
cine  virus  by  passing  the  former  through  cows. 
Abbot  quotes  W.  J.  Simpson  as  follows :  "In  ISTo- 
vember,  1885,  with  smallpox  lymph  from  an  un- 
vaccinated  patient,  ]  inoculated  a  cow  with  fifth- 
day  lymph  and  a  ewe  with  eight-day  lymph  from 


54_'  IM'KCTIOX    AMI    I  MM  (MTV. 

the  same  patient.  Both  i)i'esentetl  vesicles  on  tlio 
seventli  dav,  the  lymph  of  which  I  sent  to  London 
to  be  used  by  Dr.  Cory,  the  direi-tor  of  thi-  Animal 
Yacciiic  Institute  of  London.  This  call'  lym[)h, 
which  Dr.  Cory  passed  through  a  second  calf  before 
using  it  on  children,  was  the  starting  point  of  a 
now  vaccine  at  the  institute.  Between  Xov.  21, 
1885.  and  May  6,  1886,  1,247  children  had  l)een 
vaccinated  with  this  lymph  and  gave  98.4  per 
cent,  insertions  of  success." 

Concerning  the  changes  which  smallpox  virus 
undergoes  in  the  cow,  as  a  result  of  which  it  loses 
permanently  the  power  of  causing  smallpox  in 
man,  we  have  no  knowledge,  aside  from  the  hy- 
])othesis  of  Councilman  and  others  mentioned  below. 

Etiology.  We  may  pass  over  the  various  bacilli  and  cocci 
whicli  have  been  described  as  causing  vaccinia  and 
smallpox  with  the  remark  that  none  of  them  are 
of  primary  significance,  but  that  they  have  been 
either  accidental  contaminations  or  the  causes  of 
secondary  infections  during  the  course  of  the  dis- 
ease. 

Theories.  There  are  two  chief  theories  as  to  tin'  cause  of 
smallpox  (and  vaccinia)  to-day.  One,  that  the  virus 
is  an  ultra-microscopic  and  uncultivatable  organ- 
ism ;  and  a  second,  that  it  is  represented  by  certain 
protozoon-like  bodies  seen  in  the  specific  lesions 
(vesicles,  pustules)  of  both  vaccinia  and  smallpox. 
Concerning  the  first  theory  we  know  nothing  be- 
yond the  observation  of  Parke  that  the  virus  of  both 
vaccinia  and  variola  did  not  pass  through  Berke- 
feld  and  Chamberland  filters  under  the  conditions 
of  his  experiments.  Of  the  second  theory  a  brief 
review  may  be  given. 

Protozoon-like  bodies  have  been  seen  by  many 


SMALLPOX    AND    VACCIMA.  543 

observers  and  were  lirst  brought  into  causal  rela-  Cytoryties 
tion  with  smallpox  by  Van  der  Loeff  and  by  L.  Proto/oom?; 
Pfieffer  (1887).  Griiarnieri  (1892),  however,  gave 
the  subject  its  present  impetus  by  a  careful  study 
of  these  forms  as  seen  in  vaccinia  and  gave  to  the 
hypothetical  organism  the  name  of  Cytoryctes  vac- 
cinice,  s.  variola'.  The  bodies  were  found  within 
the  deep' epithelial  cells  in  the  pustules  of  vaccinia 
and  smallpox  and  in  the  lesions  produced  on  the 
cornea  of  the  rabbit  by  inoculation  with  the  viruses 
of  vaccinia  and  smallpox.  They  lie  within  clear 
spaces  in  the  protoplasm  of  the  cells,  vary  in  size 
from  that  of  a  micrococcus  to  that  of  an  epithelial 
nucleus  and  multiply,  it  was  supposed,  by  binary 
division.  When  mounted  in  hanging-drops  of  the 
vesicular  fluid  they  showed  ameboid  movements. 
Confirmatory  work  came  from  others,  and  partic- 
ularly Wasielewski,  who  concluded  that  the  "vac- 
cine bodies"  are  perfectly  characteristic,  that  they 
are  never  found  in  normal  or  other  pathological 
conditions  of  the  skin,  that  they  can  not  originate 
from  leucocytes  or  epithelial  cells,  and  hence  can 
not  be  accidental  "cell  inclusions."  Filtered  virus 
produced  no  lesions  in  the  cornea  of  the  rabbit. 

Eecently  Councilman,  Magrath  and  Brincker-  Work  of 
hoff  have  studied  this  supposed  organism  in  great  and  others. 
detail  and  find,  in  addition  to  the  forms  in  the  cy- 
toplasm (cytoplasmic  parasites), 'still  others  within 
the  nucleus  of  the  epithelial  cells  of  the  vesicles 
and  pustules.  They  express  the  belief  that  the  or- 
ganism first  gains  entrance  in  the  cytoplasm  of  the 
cells,  and  after  a  period  of  "multiplicative  prolif- 
eration," the  products  of  the  latter  process  pene- 
trate the  nuclei  of  the  epithelial  cells  and  there 
undergo   another  type  of  proliferation.     Calkins, 


544 


IMECTIOX    AM)    IMMLMTY. 


I  ife  History 
of  Cytoryctes. 


the  zoologist,  after  studying  the  material,  shares 
their  views  and  has  constructed  a  life  cycle  of  the 
parasite  from  the  various  forms  Avliieh  lie  found  in 
fixed  and  stained  preparations. 

The  smallest  recognizable  forms  in  the  cytoplasm 
measure  about  0.7  of  a  micron  and  lie  in  a  vacuole  in 
the  cj'toplasm  near  the  nucleus.  Calkins  interprets 
these  as  "gemmules"  and  as  products  of  the  prolifera- 
tion of  the  parasite  at  the  primary  point  of'  infection 
(lungs  (?)  ).  Somewhat  larger  forms  (3  microns)  con- 
taining a  vacuole  with  a  central  point  staining  with 
methylene  blue,  represent  "gemmules"  which  have  grown 
and  have  become  somewhat  differentiated.  The  periphery 
Cytoplasmic  of  the  organism  becomes  diU'ercntiated  also  by  the  for- 
Stages.  niation  of  minute  dots  which  may  eventually  be  stained 
by  a  special  method.  During  this  stage  the  organism 
"often  is  spherical,  but  may  be  fusiform,  pyriform  or 
ameboid,  while  pseudopodia  are  frequentlj'-  caught  in 
various  degrees  of  extension."  No  definite  nucleus  is 
discernible,  but  material  corresponding  to  nuclear  sub- 
stance is  distributed  somewhat  generally  through  the 
parasitic  cell.  Certain  granules  are  distributed  through- 
out the  body  of  the  organism,  and  these  granules  eventu- 
ally give  rise  to  the  "gemmules"  or  young  parasites 
which  become  free  by  the  disintegration  of  the  mother 
cell. 

Howard  and  Perkins  find,  in  addition  to  the  cyto- 
plasmic stage  of  Councilman  and  his  co-workers,  a  sec- 
ond cytoplasmic  stage,  the  products  of  which  penetrate 
the  nucleus  to  institute  the  intranuclear  stages.  Cal- 
kins speaks  of  the  fate  of  the  gemmules  as  follows: 
"The  germs  formed  by  the  multiplicative  reproduction 
of  the  cytoplasmic  "ameboid  form  of  the  parasite  may 
develop  into  new  cytoplasmic  organisms  or  ultimately 
may  become  germ  cells  within  the  nucleus  of  the  epithe- 
lial cell.  In  the  latter  case  they  develop  into  struc- 
tures which  I  regard  as  gametocytes.  The  resulting 
zygote  (formed  by  conjugation  of  the  gametes)  is  the 
ameboid  pansporoblast  mother  organism." 
Nuclear  The  conclusion  that  conjugation  takes  place  is  based 
Stages.  ^^  certain  analogies  with  other  micro-organisms,  rather 
than    on    observation    of   the    phenomenon.      This   intra- 


SMALLPOX    AND    VACCINIA.  545 

nuclear  mother  organism,  the  product  of  conjugation, 
finally  grows  to  a  size  of  10  to  12  microns  and  forms 
within  it  from  eight  to  twenty  "primary  sporoblasts." 
The  young  sporoblasts  are  eventually  liberated  from  the 
mother  cell  and  are  at  first  solid  and  homogeneous,  like 
the  gcmmules,  but  later  when  they  have  reached  a  size  of 
li/o  to  2  microns  small  vacuoles  appear  in  the  peripheral 
ring  of  substance  and  in  each  vacuole  a  young  spore  is 
formed.  The  formation  of  these  spores  terminates  the 
"primary  nuclear  phase"  of  the  organism.  These  spores, 
still  Avithin  the  nucleus  of  the  epithelial  cell,  become, 
in  their  turn,  sporoblasts,  and  the  formation  of  a  large 
number  of  secondary  spores  within  them  constitutes  the 
secondary  nuclear  phase  of  the  parasite.  In  the  mean- 
time the  nucleus  of  the  epithelial  cell  has  degenerated, 
and  the  secondary  sporoblast  with  its  contained  spores 
escapes  first  into  the  cytoplasm  and  eventually  into  the 
pericellular  space.  In  accordance  with  this  conception 
the  intranuclear  process  is  well  calculated  to  give  rise 
to  a  massive  number  of  young  parasites  within  the  body. 
Councilman,  Magrath  and  Brinckerhoflf  state  that  after 
the  tenth  day  of  the  disease  the  parasites  become  more 
and  more  difficult  of  recognition  by  microscopic  methods. 
However,  Brinckerhoff  found  that  even  the  desiccated 
crusts  of  pustules  and  vesicles  produce  typical  lesions 
on  the  cornea  of  the  rabbit.  These  forms  have  never 
been  recognized  positively  in  the  blood  of  patients,  and 
Magrath  and  Brinckerhoff  were  not  able  to  produce  le- 
sions in  the  rabbit's  cornea  by  inoculation  of  variolous 
blood.  The  general  distribution  of  the  lesions  in  the 
skin  and  the  occurrence  of  fetal  smallpox  gives  us  abun- 
dant reason  for  believing  that  the  blood  stream  is  in- 
vaded  by   the   jDarasites. 

It  was  stated  above  that  bodies  of  the  general  nature  Cytoryctes  in 
of  those  described  are  found  in  vaccinia  as  well  as  in  ^^ccinia. 
smallpox,  and  this  occurrence  is  some  added  reason  for 
believing  that  Cytoryctes  variolw,  s.  vaccinkv.  is  the 
cause  of  these  processes.  It  is  a  most  interesting  and 
important  observation  by  the  American  authors  cited 
that  the  intranuclear  stage  of  the  parasite  does  not 
occur  in  vaccinia  (Tyzzer),  and  we  are  led  to  believe 
that    this    is    an    important    differential    point    between 


54G 


IXFECTIOX    AXD    niMVyiTY. 


Infection 
Atrium. 


Dissemination. 


vaccinia  and  smallpox.  Assuming  that  the  bodies  in 
question  cause  the  disease,  the  thought  is  pei-tinent  that 
the  dilTerence  in  virulence  between  vaccinia  and  variola 
inocuhita  may  depend  on  the  failure  of  (he  intranuclear 
cycle   to  appear   in   vaccinia. 

The  work  of  Giiariiieri,  and  particularly  that  of 
Councilman,  Magrath  and  Brinckerhoff,  is  most 
suggestive,  and  ardent  supporters  of  their  views 
have  appeared  with  corroborative  work  (e.  g.,  How- 
ard). At  the  same  time  man}^  skilled  observers 
discredit  entirely  the  parasitic  nature  of  the  bodies 
described,  interpreting  them  rather  as  products 
of  degeneration  of  the  epithelial  cells  and  nuclei 
or  as  inclusions  of  other  tissue  cells  (e.  g.,  leuco- 
cytes, Borrel)  or  fragments  of  other  nuclei.  Ewing 
expresses  similar  views.  The  state  of  the  question 
is  sueli  that  I'nrther  study  is  urgently  called  for. 

We  have  no  positive  knowledge  as  to  infection 
atrium  in  smallpox,  although  the  existence  of  a 
"contagious  zone''  of  atmosphere  about  the  patients 
is  good  ground  for  the  belief  that  invasion  takes 
place  through  the  respiratory  passages.  The  disease 
which  follows  introduction  of  the  virus  into  the 
skin  is  spoken  of  as  variola  inoculata,  and  is  much 
less  severe  than  smallpox.  We  are  also  ignorant  to 
a  large  degree  of  the  means  of  excretion  or  dissem- 
mination  of  the  virus.  Osier  states  that  the  virus 
"exists  in  the  secretions  and  excretions  and  in  the 
exhalations  from  the  lungs  and  skin."  The  dried 
epithelial  cells  which  are  continuously  thrown  off 
are  no  doubt  a  most  important  means  of  dissemina- 
tion. Infection  may  be  transmitted  by  means  of 
clothing  or  other  materials  which  have  been  in  con- 
tact with  patients,  and  the  disease  may  be  carried 
to  others  from  the  sickroom  by  a  healthy  person. 


(SMALLPOX    AND    VACCINIA.  547 

Epidemiologic  experience  teaches  that  the  virus  is 
one  of  great  resistance  and  tenacity. 

The  incubation  period  in  variola  falls  within  the  Cyclic  Nature 
extremes  of  eight  to  twenty  days,  most  commonly 
from  nine  to  fifteen  days.  The  stage  of  invasion, 
or  the  primary  fever,  terminates  the  incubation 
period,  and  during  this  time  the  initial  rash  ap- 
pears, accompanied  by  moderate  hyperleucocytosis. 
On  the  third  to  the  fourth  days  the  remission  sets 
in,  the  number  of  leucocytes  in  the  blood  decreases 
to  normal  or  below  normal,  and  cutaneous  lesions 
make  their  appearance,  and  in  the  course  of  forty- 
eight  hours  show  a  vesicular  nature.  When  the 
umbilicated  vesicles  are  changed  into  pustules  the 
temperature  again  rises  (secondary  fever)  and  hy- 
perleucocytosis again  develops.  This  much  only 
of  the  clinical  picture  is  mentioned  to  emphasize 
the  cyclic  nature  of  the  phenomena ;  one  may  well 
suspect  that  the  organism  causing  such  a  disease 
undergoes  particular  phases  of  development  which 
in  some  way  are  related  to  the  well-known  clinical 
cycle. 

Epidemics  are  sometimes  of  so  mild  a  charac-  variations  in 

^  Virulence. 

ter  that  the  patients  are  not  bed-ridden  and  may 
be  found  in  the  pursuit  of  their  occupations  in 
spite  of  well-marked  eruptions.  Such  occurrences 
can  be  referred  only  to  a  virus  of  low  pathogeni- 
city. Even  mild  epidemics,  however,  may  be  ac- 
companied by  severe  and  fatal  cases.  Cases  of  am- 
bulatory smallpox  are  most  important  factors  in 
spreading  the  disease. 

We  have  nothing  more  than  presumptive  knowl-  "l^yfrusf"" 
edge  concerning  the  distribution  of  the  virus  in  the  Body. 
the  body  aside  from  its  occurrence  in  the  skin  and 
mucous  membranes.     We  may  feel  certain,  how- 


548 


INFECTION    AND    nnilMTY. 


Secondary 
infections. 


Prophylaxis. 


Discovery  of 
Vaccination. 


ever,  that  the  infection  is  systemic.  The  lesions 
of  the  skin  are  of  such  a  nature  that  the}^  are 
generally  regarded  as  of  embolic  character,  which 
presupposes  blood  infection ;  and  transmission  of 
the  disease  througli  the  placenta  is  decisive  proof 
of  a  general  distribution  of  the  virus  at  some  stage 
of  the  process.  The  failure  to  cause  vaccinia  in 
the  cornea  of  the  rabbit  by  inoculating  the  blood 
of  i^atients  (cited  above)  may  indicate  that  the 
virus  is  present  in  the  blood  in  small  quantity  or 
that  circulating  organisms  are  eventually  de- 
stroyed. The  intoxication  of  smallpox  is  mani- 
festly general. 

In  few  diseases  does  secondary  infection  play  so 
important  a  role  as  in  smallpox.  Wlien  the  cu- 
taneous lesions  have  become  pustular  they  usually 
contain  pyogenic  cocci,  although  they  may  be  ab- 
sent. It  is  somewhat  strange  that  streptococci  are 
more  often  encountered  than  staph3dococci,  in 
view  of  the  normal  presence  of  the  latter  in  the 
epidermis.  Fatal  cases  are  almost  without  excep- 
tion accompanied  by  general  streptococcus  infec- 
tions, and  Councilman  believes  these  organisms 
are  more  important  as  a  cause  of  death  than  the 
specific  virus. 

Successful  propliylaxis  involves  universal  vac- 
cination, in  addition  to  special  measures  which  are 
demanded  in  the  presence  of  the  disease:  isola- 
tion of  the  sick  until  desquamation  is  complete, 
antiseptic  baths,  and  disinfection  and  fumigation 
as  currently  practiced. 

Interesting  matters  of  history  are  the  facts  that 
protective  inoculation  against  smallpox  Avas  prac- 
ticed in  fairly  ancient  times  by  rather  primitive 
races,   and   that   Lady   ]\Iary   Wortley   Montague 


HMALLl'OX    AND    VACCINIA.  549 

introduced  this  method  into  Europe  in  1718. 
This  was  not  the  vaccination  in  vogue  to-day, 
however,  but  rather  the  inoculation  of  virulent 
virus  from  the  pustules  of  the  diseased  into  the 
healthy.  As  mentioned  in  one  of  the  earlier  chap- 
ters, this  procedure  commonly  produced  a  mild 
type  of  disease  (variola  inoculata)  which  ren- 
dered the  individual  immune  to  virulent  small- 
pox. 

Everyone  knows  that  the  vaccination  of  to-day, 
i.  e.,  the  substitution  of  the  virus  of  cowpox  for 
that  of  smallpox,  was  the  discovery  of  Jenner 
(1798),  and  we  need  offer  no  comments  concern- 
ing its  efficacy  nor  repeat  the  well-earned  epithets 
which  have  been  applied  to  the  rare  species  of  dis- 
believers. Nothing  is  more  certain  than  that 
smallpox  has  ceased  to  be  a  world  pest  only  be- 
cause of  the  continued  Jennerization  of  the  race. 

The  essential  points  established  by  Jenner  are 
the  following:  1.  That  the  vaccine  disease 
■casually  communicated  to  man  has  the  power  of 
rendering  him  insusceptible  to  smallpox.  2.  That 
the  specific  co^^vpox  alone,  and  not  other  eruptions 
affecting  the  cow  which  might  be  confounded  with 
it,  has  this  protective  power.  3.  That  the  cow- 
pox  may  be  communicated  at  will  from  the  cow  to 
man,  by  the  hand  of  the  surgeon,  whenever  the 
requisite  opportunity  exists.  4.  That  the  cowpox,. 
once  engrafted  on  the  human  subject,  may  be  con- 
tinued from  individual  to  individual  by  successive 
transmissions,  conferring  on  each  the  same  im- 
munity against  smallpox  as  was  produced  in  the 
one  first  infected  directlv  from  the  cow  (cited 
from  S.  W.  Abbott). 

For  at  least  half  a  centurv  following  Jenner's 


Jenner. 


550 


INFECTION    A\n    1)1)11  WITY. 


Humanized 
L>mph. 


Cowpox. 


Preparation 
of  Vaccine. 


discovery  humanized  lymph  was  used  for  vacci- 
nation, new  patients  being  inoculated  by  means 
of  points  prepared  from  vesicles  of  previous  cases, 
or  with  the  fresh  lymph  from  such  cases.  The  not 
infrequent  transmission  of  syphilis  by  this  means 
was  the  source  of  many  calamities.  Following  the 
precedent  of  Warlemont  in  1868,  the  lymph  of 
cowpox  is  now  the  universal  source  of  vaccine. 

Cowpox  probably  occurs  to  a  greater  or  less 
degree  in  all  countries,  especially  in  the  spring  and 
summer,  attacks  the  udder  and  teats  almost  ex- 
clusively, and  is  accompanied  by  very  mild  con- 
stitutional symptoms.  The  incubation  period  is 
from  three  to  eight  days.  There  is  first  local 
heat,  swelling  and  tenderness,  followed  by  the  for- 
mation of  papules,  which  in  three  or  four  days 
after  their  appearance  are  transformed  into  vesi- 
cles. The  disease  reaches  its  maximum  develop- 
ment at  the  tenth  or  eleventh  day,  the  umbilicated 
vesicles  going  through  the  usual  course  to  crust 
formation. 

Calves  and  heifers  from  the  age  of  two  months 
to  two  years  are  best  suited  for  vaccination  in  the 
production  of  lymph  for  commercial  purposes. 
The  region  of  the  flank  or  the  Avhole  ventral  sur- 
face of  the  body  may  be  inoculated,  and  in  the  lat- 
ter instance  as  many  as  a  hundred  or  more  inser- 
tions may  be  made.  The  skin  is  first  shaved, 
cleansed  with  antiseptics,  and  the  lymph  from  an- 
other calf  is  introduced  by  means  of  a  syringe  or 
by  scarification.  In  some  institutions  long,  very 
superficial  parallel  incisions  are  made  and  the 
virus  rubbed  in  with  a  spatula.  Within  five  days 
to  a  week  the  vesicles  are  in  such  condition  that 
thp  Ivmph   may  be  collected,  the  contents  either 


SMALLPOX    AND    VACCINIA. 


551 


being  squeezed  out  with  suitably  formed  forceps 
or  scooped  out  with  a  sharp  spoon.  Depending  on 
the  area  vaccinated,  the  lymph  collected  from  a 
single  calf  may  be  sufficient  for  from  2,000  to 
15,000  vaccinations  in  man.  In  view  of  tlio  im- 
munity which  is  conferred  calves  can  l)e  used  but 
once  for  the  production  of  vaccine  virus. 

All  other  methods  of  preserving  lymph  have 
been  largely  abandoned  for  the  process  of 
giycerinization,  the  glycerin  being  very  inti- 
mately mixed  with  the  virus  by  mechanical 
means  and  allowed  to  remain  in  this  state  in 
a  cool  place  for  from  six  to  eight  weeks  before 
the  product  is  put  on  the  market.  Dried  vaccine 
on  ivory  jooints  is  still  used  to  some  extent,  the 
points  being  coated  directly  from  the  vesicles. 
Dried  vaccine  retains  its  power  for  from  two  to 
four  months  or  longer  when  kept  in  a  cool,  dark, 
dry  place.  Glycerinated  lymph  has  many  advan- 
tages, the  most  important  of  which  relates  to  the 
bactericidal  action  of  the  glycerin  by  which  the 
lymph  is  freed  from  the  pathogenic  bacteria  (e.  g., 
staphylococci)  which  in  former  times  caused  ser- 
ious complications  in  vaccination.  The  glycerin 
is  supposed  to  destroy  such  organisms  to  a  large 
degree  without,  however,  injuring  the  vaccine 
virus  itself.  It  is  also  stated  that  glycerinated 
lymph  is  much  more  durable  than  the  dried ;  that 
its  potency  may  be  retained  for  eight  months  or 
longer  under  suitable  conditions.  Eosenau  has 
recently  called  attention  to  the  fact  that  the  bac- 
tericidal power  of  glycerin  has  been  overestimated, 
and  that  while  it  kills  pyogenic  cocci  within  two 
weeks  when  at  the  body  temperature,  such  organ- 
isms may  live  for  months  in  glycerin  when  in  the 


Giycerinization. 


Effect  en  Con- 
taminating 
Bacteria. 


o^rl  IXrJX'TfOX    A\n    /l/l/r\77'V. 

ice  chest ;  aud^  of  course,  ouv  glycerinated  virus 
is  kept  in  the  ice  chest.  Tetanus  spores  live  for 
months  in  glycerin  and  glycerin  lias  practically 
no  neutralizing  action  on  tetanus  toxin.  Glycerin 
docs  liave  tlio  power,  however,  of  attenuating  the 
tetanus  spores,  and  its  slow  bactericidal  action  is 
well  established.  As  stated  above,  the  vaccine 
should  be  gl3'cerinized  for  some  weeks  before  it  is 
put  on  the  market.  Glycerin  has  the  added  ad- 
vantage for  the  manufacturer  of  enal)ling  him  to 
dilute  his  lymph  moderately  (50  to  GO  per  cent.) 
without  impairing  the  virus. 

Of  much  more  importance  for  the  safety  of 
virus  than  glycerinizatidn  arc  pi'npci-  hygiene  and 
cleanliness  during  the  whole  process  of  prepara- 
tion. The  powers  recently  conferred  on  the  Sur- 
geon-General by  an  act  of  Congress  have  resulted 
in  a  great  improvement  in  the  purity  of  the  vac- 
cine now  on  the  market.* 

While  it  can  not  be  expected  that  vaccine  will 
be  entirely  free  from  bacteria,  it  is  possible  to  re- 
duce their  number  to  a  low  minimum  and  to  elim- 
inate pathogenic  forms,  particularly  pathogenic 
cocci,  tetanus  and  tubercle  bacilli. 
Vaccination  The  tcclinic  of  vaccination  is  so  well  known 
that  no  description  is  needed.  It  need  only  be 
stated  that  in  scarifying  it  is  undesirable  to 
cause  hemorrhage  and  that  the  operation  is  a  sur- 
gical ijrocedure,  demanding  surgical  cleanliness 
and  surgical  care  of  the  wound.  As  a  rule  vac- 
cination in  man  protects  against  smallpox  for  a 
period  of  six  to  ten  years,  after  which  revaccina- 
tion    is    necessary  for    continued  protection.     It 

*  John  F.  Anderson  "Federal  Control  of  Vaccine  Virus," 
Jour,  of  the  Amer.  Med.  Assn.,  June  10,   1905. 


SMALLI'O.y    AM)     VACCIMA.  553 

should  not  be  concluded  from  the  negative  out- 
come of  a  single  vaccination  that  the  individual  is 
immune  to  vaccination  and  hence  immune  to 
smallpox,  but  rather,  repeated  attempts  should  be 
made  with  virus  known  to  be  fresh.  It  is  quite 
possible  that  certain  individuals  are  immune  to 
vaccinia,  as  often  stated,  but  they  are  very  rare, 
and  the  condition  should  not  be  recognized  hastily. 
Among  38,000  vaccinations  Dr.  Cory  encountered 
but  one  in  which  a  "take"  could  not  be  gotten  on 
second  trial  (Abbott). 

The  ideal  condition  is  that  all  children  should  when  to 

Vaccinate. 

be  vaccinated  at  an  early  age  by  requirement  of 
law  as  in  certain  European  countries,  where  it  is 
demanded  within  the  first  few  months  or  the  first 
year  or  two  of  life.  Some  countries  require  re- 
vaccination  before  the  children  are  admitted  to 
school  and  recommend  repetitions  at  suitable  in- 
tervals. 

We  have  no  national  law  on  the  subject  and  the 
state  laws  differ.  In  many  states  children  must 
be  vaccinated  before  they  are  admitted  to  the  pub- 
lic schools,  the  responsibility  sometimes  falling 
on  the  school  and  sometimes  on  the  city  or  tc^Ti 
authorities.  A  number  of  states  have  no  laws  on 
the  subject,  although  vaccination  is  for  the  most 
]3art  assvired  through  the  requirements  of  the 
State  Boards  of  Health  and  the  local  authorities. 

When  there  is  danger  of  an  epidemic,  and  in 
known  cases  of  exposure,  vaccination  should  be 
practiced  thoroughly.  Inasmuch  as  the  incuba- 
tion period  of  vaccinia  is  about  three  days  less 
than  that  of  smallpox,  successful  vaccination  pro- 
tects within  a  limited  period  following  exposure. 
Immediate   vaccination   is    demanded   in    case   of 


554 


INFECTIOy    A\n    IMMLMTY. 


Imniunity  and 
Susceptibility. 


Leucocytes. 


Serum. 


exposure.  Healthy  infants  may  be  vaccinated 
within  the  first  six  weeks  or  two  months  of  life 
and  at  any  earlier  period  in  case  of  exposure. 

An  attack  of  smallpox  confers  prolonged  and, 
with  few  exceptions,  lasting  immunity.  Second 
and  even  third  attacks  have  been  described.  It  is 
known  that  those  who  have  had  smallpox  may  be- 
come susceptible  to  vaccination  after  a  period  of 
time.  Susceptibility  varies  a  good  deal  with  age. 
During  the  ages  of  from  two  to  fourteen  years 
the  disease  is  less  common  than  between  fifteen 
and  forty,  and  after  this  period  it  again  decreases 
in  frequency.  Undoubted  instances  of  natural 
immunity  to  smallpox  occur,  but  they  are  very 
rare. 

Smallpox  is  accompanied  by  a  leucocytosis 
wliich  is  peculiar  because  of  the  large  number  of 
mononuclears.  There  is  a  slight  rise  in  the 
number  of  leucocytes  during  the  first  febrile  on- 
set, a  fall  to  almost  normal  during  the  remission, 
followed  by  a  second  rise,  which  may  be  as  high 
as  16,000  to  20,000.  Fatal  cases  show  a  terminal 
hypoleucocytosis  (]\Iagrath,  Brinckerhoff  and  Ban- 
croft). Large  numbers  of  lymphocytes  are  also 
found  in  the  pustules  (Eoger).  ISTothing  of  a  sat- 
isfactory nature  is  known  concerning  the  relation- 
ship of  the  leucocytes  to  recovery  and  immunity. 

There  is  no  serum  therapy  for  smallpox.  The 
interesting  observation  has  been  made,  however, 
that  the  serum  of  convalescents  or  of  vaccinated 
man  or  animal  will,  when  mixed  with  vaccine 
virus,  prevent  its  action. 

Horsepox  is  identical  with  cowpox.  Sheeppox 
(clavel6e)  is  an  independent  disease.  The  virus  of  cow- 
pox  produces  a  local  lesion   in  the  sheep,  but  does   not 


CHICKENPOX.  555 

cause  immunity  to  sheeppox.  The  virus  of  sheeppox,  on 
the  other  hand,  has  no  effect  on  horses  and  cattle 
(Nocard  and  Leclainche).  The  virus  of  sheeppox  is 
filterable    ( Borrel ) . 

VIII.    CHICKENPOX     (vAEICELLA), 

Although  the  skin  manifestations  of  varicella 
often  resemble  those  of  smallpox  to  such  an 
extent  that  differentiation  is  difficult,  the  two 
diseases  are  distinct.  Nothing  indicates  this  more 
clearly  than  the  fact  that  one  who  has  recovered 
from  varicella  is  susceptible  to  vaccination,  and  it 
is  loiown  further  that  an  attack  of  chickenpox 
does  not  protect  against  smallpox. 

The  etiology  is  unknown,  and  no  organism 
which  has  been  described  can  be  considered  the 
probable  cause. 

Varicella  occurs  epidemically  and  sporadically. 
The  virus  probably  exists  in  the  lesions  of  the 
skin  and  in  the  scales,  and  the  latter  may  be  the 
chief  source  of  contagion.  There  is  no  definite 
knowledge  concerning  the  resistance  of  the  virus, 
nor  its  distribution;  the  conclusion  is  justified, 
however,  that  it  exists  in  the  circulation  at  least 
in  an  early  stage  of  the  disease.  The  infection 
atrium  likewise  is  a  matter  of  conjecture,  but 
probably  is  to  be  found  in  the  lungs  or  upper 
respiratory  tract. 

The  patients  should  be  isolated  and  school  chil- 
dren should  not  be  allowed  to  return  to  school 
until  desquamation  is  complete.  Disinfection 
should  be  practiced. 

•  Susceptibility  and  virulence  wo\ild  seem  to  vary, 
since  the  severity  of  the  cutaneous  lesions  is  not 
constant.  In  delicate  and  tuberculous  children, 
the  lesions  may  become  gangrenous.    Hemorrhagic 


55(;  i\i'i:(Ti()\    i\7>   nnii  \//v. 

varicella  is  observed  oceasionally.  Such  compli- 
cations as  nephritis  and  otitis  media  occur. 

Varicella  is  a  disease  of  childhood,  although  it 
may  occur  in  adults.  Infants  are  attacked  less 
frequently.  Second  or  even  third  attacks  occur, 
although  they  are  rare. 

There  is  no  serum  therapy. 

IX.    SCAELET  FEVER. 

The  role  -which  the  streptococcus  plays  in  scarlet 
fever  was  considered  on  page  361. 

The  ^'TDodies"  recently  observed  by  Mallory  may 
be  referred  to  briefly. 
TheProto-  In  1903  Mallory  described  certain  protozoon- 
'**Maiiory.  Hkc  Ijodics  found  in  the  skin  of  four  cases.  They 
could  be  divided  into  two  groups,  one  of  which 
consisted  of  "round,  oval,  elongated,  lobulated 
bodies"  from  2  to  7  microns  in  diameter ;  the  indi- 
viduals of  the  second  group  "contain  a  central 
round  body,  around  which  are  grouped,  on  optical 
section,  from  10  to  18  narrow  segments,  which,  in 
some  cases,  are  united,  but  in  others  are  sharply 
separated  laterally  from  each  other."  They  occur 
within  and  between  the  epithelial  cells  and  in  the 
superficial  part  of  the  corium.  He  gives  the  name 
of  Cydaster  scarlatinal  is  to  these  bodies,  and,  al- 
though expressing  the  belief  that  they  are  protozoa 
and  have  a  causal  relation  to  scarlet  fever,  does  not 
claim  to  have  proved  such  a  relation. 

Duval  corroborated  the  discovery  of  Mallory, 
and  demonstrated  the  bodies  in  five  out  of  eighteen 
cases  in  blisters  which  were  produced  artificially 
during  the  height  of  the  eruption.  Field  found 
them  not  only  in  the  skin  of  scarlet  fever,  but  also 
ill   tliat   of  measles   and   concludes  that  manv  of 


HCARLET    FEVER. 


557 


them  at  least  represent  artifacts  or  degeneration 
forms  of  tissue  cells.  More  extensive  observations 
seem  to  be  necessary  to  establish  the  nature  of 
these  supposed  parasites. 

Other  micro-organisms  which  have  been  de- 
scribed as  the  cause  of  scarlet  fever,  including  the 
Diplococcus  scarlatince  of  Class,  we  may  pass  over 
with  the  remark  that  the  claims  concerning  them 
have  not  been  upheld. 

The  contagiousness  of  scarlet  fever  is  extreme,  ^^j^j^an"-"* 
and  the  virus  undoubtedly  is  thrown  into  the  sur-  mission. 
rounding  air  from  the  skin  of  the  patient.  It  is 
highly  probable  that  the  virus  also  reaches  the  sur- 
rounding air  from  the  respiratory  passages  by 
means  of  "drop  infection,"  since  transmission  may 
occur  before  the  skin  shows  involvement.  Patients 
continue  to  be  infectious  for  from  4  to  6  weeks  or 
longer  after  the  appearance  of  the  eruption.  The 
disease  may  be  transmitted  by  an  intermediate 
healthy  person,  or  by  contaminated  clothing  or 
furnishings.  The  origin  of  epidemics  from  milk 
which  has  in  some  way  been  contaminated  seems 
to  have  been  proved  in  a  number  of  instances. 

Of  great  importance  for  the  persistence  of  an 
epidemic  is  the  resistance  of  the  virus,  which  re- 
mains viable  and  virulent  for  months  and  possibly 
for  years,  when  under  suitable  conditions. 

Prophylaxis  demands  isolation  of  the  patients  Prophylaxis. 
until  desquamation  is  complete;  the  use  of  anti- 
septic baths  or  ointments,  or  vigorous  scrubbing 
with  soap  as  desquamation  proceeds;  antiseptic 
treatment  of  the  mouth  cavity;  disinfection  of  all 
utensils,  linen,  etc.,  with  which  the  patient  has 
been  in  contact ;  avoidance  of  stirring  up  the  dust 
in  the  room,  Avhich  demands  moist  rather  than  dry 


558 


l.\J'JX"J10.\     AM)    IMML.MTY. 


Susceptibility 
and  Immunity. 


Leucocytes. 


Serum 
Therapy. 


cleansing;  the  disinfection  of  the  sputum  and 
other  discharges  of  the  patient;  an  abundance  of 
f  resli  air  and  sunshine  in  tlie  sick  room ;  tlie  final 
disinfection  of  the  room.  Physicians  and  nurses, 
when  in  the  presence  of  the  patient,  should  wear 
long  gowns,  which  can  he  discarded  on  leaving, 
and  other  Avell-known  precautions  should  be  ob- 
served to  avoid  spreading  of  the  disease. 

Scarlet  fever  is  particularly  a  disease  of  clii Id- 
hood,  "a  large  proportion  of  cases  occurring  before 
the  tenth  year"  (Osier).  Adults  are  attacked  not 
infrequently.  Infants  are  less  susceptible  than 
older  children.  Many  examples  of  family  immun- 
ity, which  probably  is  relative,  are  encountered, 
and  likewise  instances  in  which  there  is  a  family 
susceptibility.  In  a  given  family  examples  of  in- 
dividual immunity  and  susceptibility  are  fre- 
quently met  with.  One  attack  usually  confers  im- 
munity against  a  second,  but  not  invariably. 

Scarlatina  is  characterized  by  a  leucocytosis, 
the  degree  of  which  bears  some  relation  to  the 
severity  of  the  infection.  In  mild  cases  the  aver- 
age is  from  10,000  to  18,850  (Bowie),  in  moder- 
ately severe  cases  from  20,000  to  40,000,  or  even  as 
high  as  78,000  (Klotz)  ;  in  malignant  uncompli- 
cated cases  there  is  a  tendency  to  a  low  leucocyto- 
sis (Klotz).  How  much  of  this  leucocytosis  de- 
pends on  co-existing  streptococcus  infection  re- 
mains "uncertain. 

Treatment  with  antistreptococcus  serum  is  the 
only  serotherapeutic  measure  which  has  been  ad- 
vocated in  relation  to  scarlet  fever.  This  is  done 
either  on  the  assumption  that  the  disease  is  of 
streptococcus  etiology,  satisfactory  proof  of  which 
has  not  yet  been  obtained,  or  with  the  hope  that 


MI'JAHfjEH. 


551) 


the  serum  will  iuUuencc  favorably  secondary  in- 
fections with  the  streptococcus.  The  serums  of 
Aronson,  Moser  and  of  Menzer  have  been  tried 
more  than  others.  Moser  is  probably  more  enthu- 
siastic than  others,  and  he  claims  a  reduction  in 
the  mortality  from  an  average  of  13.08  per  cent, 
to  8.9  per  cent,  in  400  cases.  Others  have  observed 
a  favorable  influence-  in  some  cases,  but  the  re- 
sults are  not  uniform.  The  development  of  sec- 
ondary streptococcus  infections  can  not  be  pre- 
vented by  the  use  of  the  serums,  although  it  is 
stated  that  their  severity  may  be  moderated. 

Of  theoretical  interest  is  the  report  by  Weiss- 
becker  and  by  v.  Leyden  that  the  serum  of  con- 
valescents causes  a  reduction  of  the  temperature 
and  a  shortening  of  the  course  of  the  disease. 

The  results  published  up  to  the  present  time 
indicate  that  we  have  not  as  yet  an  efficient  serum 
for  scarlet  fever  (see  also  p.  367). 

X.    MEASLES. 

Bacilli  which  have  been  recognized  in  the  con-  Micro- 

,  .  J  -,  ^  p    organisms. 

]unctiva,  sputum  and  nasal  passages  m  cases  oi 
measles  have,  for  the  most  part,  resembled  either 
the  diphtheria  or  the  influenza  bacillus.  Pseudo- 
diphtheria  bacilli  are  normal  residents  in  the  eye, 
and  influenza-like  bacilli  are  found  in  the  sputum 
in  various  conditions;  hence,  there  is  insufficient 
reason  to  associate  such  organisms  with  the  etiol- 
ogy of  measles.  The  micrococci  found  by  Lasage 
(1900)  have  not  received  recognition  as  the  cause 
of  the  disease. 

Measles  is  highly  contagious,  even  during  the  Distribution  of 

.  *  the  Virus 

prodromal  stage.  The  contagion  doubtless  is  ex- 
creted from  the  lungs  as  well  as  the  skin,  and.  in 


oUO  IXFECTIOX    .l.\7>    LMMl  MTV. 

view  of  the  early  broueliial  syinptoms,  the  virus 
probably  gains  entrance  through  the  lungs.  Suc- 
cessful inoculation  into  man  with  blood  taken 
from  the  involved  skin  shows  that  the  virus  exists 
in  the  circulation  of  the  skin.  Hektoen  doubts 
the  decisiveness  of  a  number  of  these  experiments 
since  they  were  carried  out  in  the  presence  of 
epidemics  and  natural  infection  could  not  be  ex- 
cluded; at  the  same  time  he  does  not  question  the 
results  of  Mayr  (1852) .  In  two  experiments  on  man 
Hektoen  determined  the  presence  of  the  virus  in  the 
blood.  ''The  results  of  these  two  experiments  per- 
mit the  conclusion  that  the  virus  of  measles  is 
present  in  the  blood  of  patients  with  typical 
measles  some  time  at  least  during  the  first  30 
hours  of  the  eruption;  furthermore,  that  the  virus 
retains  its  virulence  for  at  least  2-i  hours  when 
such  blood  is  inoculated  into  ascites-broth  and  kept 
at  37°  C.  This  demonstration  shows  that  it  is 
not  difficult  to  obtain  the  virus  of  measles  unmixed 
with  other  microbes  and  in  such  form  that  it  may 
be  studied  by  various  methods."  The  virus  is 
much  less  resistant  than  that  of  scarlet  fever.  The 
varying  grades  of  severity  of  different  epidemics 
show  that  it  is  subject  to  alteration  in  its  virulence. 
Effect  on  Although  measles  is  considered  somewhat  harm- 
Resistance.  |^,g  ^^^  ^YiQ  whole,  dangerous  complications,  such 
as  broncho-pneumonia  and  otitis  media,  are  suffi- 
ciently frequent.  The  development  of  tuberculosis 
following  measles,  an  event  which  is  not  uncom- 
mon, shoe's  that  measles  may  greatly  decrease  gen- 
eral resistance. 
Prophylaxis.  The  prophvlaxis  of  measles  is  not  different  from 
that  of  other  exanthemata.  The  isolation  should 
continue  for  four  weeks  after  the  appearance  of  the 


MEASLES. 


501 


Susceptibility 
and  Recur- 
rence 


exanthem  (Gotschlich).  The  sickroom  sliould  bo 
disinfected  eventually.  The  view  not  uncommonly 
encountered  that  measles  is  a  good  thing  for  a 
child  to  have  and  be  over  with  is  in  no  way  justifi- 
able. The  development  of  serious  complications 
ean  in  no  case  be  foreseen,  and  fatalities  may  occur 
even  in  mild  epidemics. 

Very  young  children^  the  rachitic  and  tubercu- 
lous, and  those  in  a  poor  state  of  nutrition  should 
be  guarded  against  exposure,  for  in  them  measles 
is  often  malignant.  Infants  are  less  susceptible 
than  older  children.  Measles  occurs  in  adults  more 
frequently  than  scarlet  fever.  Eecurrences,  on  the 
whole,  are  frequent,  as  many  as  four  attacks  hav- 
ing been  noted  in  an  individual.  Hence,  the  im- 
munity caused  by  infection  is  not  uniformly  of  a 
permanent  character. 

It  is  very  probable  that  the  inhabitants  of  a 
country  in  which  measles  is  endemic  gradually 
become  immunized,  with  the  result  that  the  disease 
prevails  in  a  mild  form.  On  the  contrary,  regions 
in  which  measles  has  hitherto  been  unknown,  or 
has  been  absent  for  many  decades,  are  susceptible 
to  visitations  of  great  malignancy.  Such  epi- 
demics have  occurred  in  the  Faroe  Islands  and  in 
Iceland,  with  a  mortality  exceeded  by  few  epi- 
demic diseases. 

A  moderate  leucocytosis  is  excited  in  measles.  Leucocytes, 
"which  begins  soon  after  infection,  reaches  its 
maximum  six  days  before  the  appearance  of  the 
eruption,  and  lasts  into  the  first  part  of  the  stage 
of  invasion"  (Tiliston).  We  are  ignorant  of  the 
significance  of  this  phagocytosis. 

There  is  no  serum  therapy  for  measles.     Weiss- 


Racial 

Immunization. 


j()2  T\FEfT10\      1\7>    /)/l/r.Y/7')  . 

becker  states  tliat  tlic  serum  of  convalescents  in- 
fluences the  course  of  the  disease  favorably. 

XI.    GERMAX   MEASLES    (iJOTTIELy), 

Eotheln  is  considered  as  distinct  from  measles, 
in  spite  of  clinical  similarities.  It  is  recognized 
because  of  certain  peculiarities  in  the  eruption  and 
its  uniformly  mild  course.  Perhaps  the  strongest 
reason  for  believing  the  two  diseases  to  be  distinct 
lies  in  the  fact  that  an  attack  of  rotheln  does  not 
leave  an  immunity  against  measles. 

Eotheln  is  contagious.  Efforts  should  be  made 
to  prevent  extension,  as  in  measles,  the  methods  of 
transmission  being  the  same  in  the  two  diseases. 

XII.    WHOOPING  COUGH. 

Various  jjrotozoa  (?)  and  bacteria  (cocci  and 
bacilli)  have  been  assigned  as  the  cause  of  whoop- 
ing cough.  Many  of  the  so-called  protozoa  found 
in  the  throat  were  undoubtedly  tissue  cells  (leuco- 
cytes, ciliated  epithelium).  Among  the  cocci,  the 
diplococcus  of  Eitter  (1892)  acquired  some  promi- 
nence. He  is  said  to  have  found  it  constantly  in 
146  cases.  Investigations  by  others  failed  to  jus- 
tify his  conclusions. 
The  Influenza-       Disregarding  some  other  bacilli  which  certain 

like  Bacillus  of  j-i  i  n  j     -i     i        i     •  -i  i 

sprengierand  mvcstigators  liavc  attempted  to  bring  into  rela- 
tion with  pertussis,  we  may  note  the  essential  facts 
concerning  an  influenza-like  bacillus  which  has 
l)een  found  with  great  constancy  and  by  many 
competent  investigators  in  the  sputum  of  patients. 
First  observed  by  Sprengler  (1897)  in  pertussis 
sputum,  this  organism  or  bacilli  similar  to  it  have 
been  found  by  Czaplewski  and  ITensel,  Zusch, 
Cavasse,  Vincenzi,  Elmassian,  Luzzatto,  Arnheim, 
Jochmann    and    Kruse.   Eeyher,    Smit.    "Wollstein, 


of  Jochmann. 


W  J  J  00 /'I  NO    COUdll. 


503 


and  Davis.     The  organism  is  said  to  be  somewliat 
larger  and  thicker  than  the  true  influenza  bacillus, 
but  has  the  same  bipolar  staining  afKnity  and  the 
same  demand  for  hemoglobin  for  its  growth  in 
pure  cultures.    There  is  some  difference  of  opinion 
as  to  whether  the  organisms  described  by  these 
different   observers    are   all   identical    and    as    to 
whether  all  have  worked  with  pure  cultures.     The 
conclusion  of  Davis  would  seem  to  sum  up  the 
situation :     "With  the   exception   of   Manicatide, 
probably  all  of  the  investigators,  at  least  in  more 
recent  years,  have  been  dealing,  either  in  pure  or 
impure  cultures,  with  the  influenza-like  bacillus, 
first  described  by   Sprengler  and  later  by  Joch- 
mann."     Culturally  they  are  not  to  be  differen-   Hemophilic 
tiated  from  the  influenza  bacillus.    When  in  pure  anTsym^^ 
culture  they  demand  hemoglobin  for  their  develop-  ''"'*'*• 
ment,  although  the  amount  of  hemoglobin  may  be 
so  small  as  not  to  color  the  medium.     When  in 
mixed   culture   with   the   streptococcus,    staphylo- 
coccus, pneumococcus  and  B.  xerosis,  they  grow 
abundantly  even  in  the  absence  of  hemoglobin. 
Hence,  in  relation  to  symbiosis,  also  they  resemble 
the  influenza  bacillus.    For  symbiotic  development 
it  is  necessary  that  the  secondary  organisms  be 
living;  when  killed  or  when  the  filtrates  of  bouil- 
lon cultures  are  used,  the  "pertussis  bacilli"  are 
not  stimulated  to  growth. 

Inoculation  of  pure  cultures  on  the  mucous  Pathogenicity. 
membrane  of  the  upper  respiratory  passages  in 
various  animals,  including  the  monkey,  does  not 
produce  a  pertussis-like  infection.  The  organisms 
have,  however,  a  low  degree  of  virulence  for  ani- 
mals, particularly  the  guinea-pig.  Davis  found 
that  three  blood-agar  cultures  injected  intraperi- 


564  INFECTIOy    AM>    IMMI  MTV. 

toueally  killed  guinea-pigs  in  24:  hours  or  less. 
The  virulence  of  the  organism  is  augmented  when 
mixed  with  certain  other  bacteria.  By  injecting  it, 
mixed  witli  a  non-pathogenic  staphylococcus,  its 
virulence,  after  six  passages,  was  so  increased  that 
one  blood-agar  culture  killed  guinea-pigs  in  24 
hours  (Davis).  In  this  respect,  also,  it  resembles 
the  influenza  bacillus. 
Significance.  Inoculatcd  in  the  throat  of  an  adult,  who  pre- 
sumedly had  never  had  whooping  cough,  a  distinct 
febrile  reaction,  lasting  two  or  three  days,  devel- 
oped after  an  incubation  period  of  two  days 
(Davis).  Headache  and  pharyngitis  were  accom- 
paniments of  the  reaction  and  the  pharj^ngitis 
continued  for  at  least  four  weeks.  There  was  lit- 
tle cough,  and  it  Avas  concluded  that  the  micro- 
organism had  not  produced  whooping  cough, 
although  it  had  shown  toxic  and  infec- 
tious properties.  The  bacillus  proliferated  enor- 
mously in  the  pharynx  and  nose  and  was  still  to 
be  cultivated  after  four  weeks;  Such  an  organism 
may  well  be  an  important  factor  in  whooping 
cough,  even  though  it  is  not  the  essential  cause. 
Davis  is  inclined  to  regard  its  relation  to  whoop- 
ing cough  as  similar  to  that  of  the  streptococcus 
to  scarlet  fever — i.  e.,  a  very  important  compli- 
cating organism. 

Davis  finds  still  further  reason  for  doubting  its 
specific  relationship  to  whooping  cough  from  the 
fact  that  it  was  found  frequently  in  measles,  acute 
influenza,  epidemic  meningitis,  bronchitis,  vari- 
cella and  in  normal  throats. 

The  organism  is  disseminated  extensively  by 
coughing,  and  the  same  is  probably  true  of  the  es- 
sential virus.     Close  contact,  as  by  kissing,  or  the 


W  IIOOI'ING    COUGH.  505 

coininon  use  of  eating  utensils  is  a  means  of  trans-  Contaoious- 
mission.  Tlie  opinion  has  been  advanced  by  Weill 
and  Pclin  that  pertussis  is  contagious  only  during 
the  catarrhal  stage  of  the  disease.  "Of  ninety- 
three  non-immune  children  who  were  placed  with 
fifteen  children  who  were  in  the  convulsive  stage, 
none  became  sick"  (cited  by  Gotschlich).  This 
point  is  not  sufficiently  established,  however,  to 
warrant  modifications  of  prophylactic  measures. 
Whooping  cough  is  often  epidemic  and  is  more 
common  in  cities  where  contact  with  the  infected 
is  more  likely  to  occur  than  in  the  country.  The 
incubation  period  is  from  seven  to  fourteen  days. 

Isolation  is  more  difficult  than  in  the  more  acute 
contagious  diseases,  yet  contact  with  other  chil- 
dren should  be  avoided  as  much  as  possible,  and 
the  patients  should  be  withdrawn  from  school 
until  recovery  is  complete. 

Pertussis  is  almost  exclusively  a  disease  of  chil- 
dren, although  older  people  may  be  attacked.  Sus- 
ceptibility is  not  general.  One  attack  usually  con- 
fers immunity.  A  varying  degree  of  leucocytosia 
is  excited  by  the  infection  (13,000  to  45,000),  the 
significance  of  which  is  not  knovni.  It  is  chiefly 
mononuclear. 

Serum  therapy  for  whooping  cough  has  not  ad-  serom 
vanced  to  a  point  where  we  can  speak  with  as-  ^''°''^''^- 
surance  concerning  it.  Manicatide  (1903)  im- 
munized horses  and  sheep  with  the  organism  which 
he  cultivated  from  a  large  number  of  cases.  He 
reports  that  cure  may  be  accomplished  in  from 
two  to  twelve  days  when  the  serum  is  used  within 
the  fi.rst  fifteen  days  of  the  disease.  The  bacillus  of 
Manicatide  differs  from  the  influenza-like  organ- 
ism of  other  observers,  hence,  his  antiserum  can 


5(50  i\ri:cTi()\  w  n   nnirxirv. 

not  be  accepted  imreservedly  as  a  specific  serum 
for  whooping  cough.  Smit  found  that  an  anti- 
serum for  the  influenza-like  organism  exerted  no 
influence  on  the  disease. 

XIII.    MUMPS    (epidemic   PAROTITIS). 

Mumps  occurs  epidemically  in  children,  particu- 
larly in  schools,  in  other  institutions,  and  in  sol- 
diers confined  to  barracks.  It  is  most  frequent  in 
the  spring  and  autumn  and  probably  is  endemic  in 
large  centers  of  population.  It  is  contagious,  the 
virus  probably  being  disseminated  from  the  upper 
respiratory  passages  with  infected  droplets  of  spu- 
tum and  saliva.  The  disease  has  an  incubation 
period  of  two  to  three  weeks  and  runs  its  course 
in  from  seven  to  ten  days. 

Involvement  of  the  testis,  ovary  or  female  breast 
are  complications  to  be  feared  in  adult  life ;  "orchi- 
tis, albuminuria,  with  convulsions,  acute  uremia, 
endocarditis  and  peripheral  neuritis  are  occasional 
complications"  (Osier).  Fatal  meningitis  devel- 
ops rarely.  Very  young  infants  and  adults  are  at- 
tacked less  frequently  than  children  of  school  age. 

Patients  should  be  isolated  for  three  weeks  from 
the  time  s}Tnptoms  appear  (Gotschlich). 

One  attack  usually  establishes  protection. 

A  peculiar  form  of  parotitis  sometimes  follows 
injury  of  the  abdominal  and  pelvic  viscera,  the  so- 
called  "postoperative"  parotitis.  The  parotid 
glands  may  also  be  invaded  by  a  number  of  kno-wTi 
micro-organisms,  e.  g.,  the  pneumococcus. 


cAPPENDIX, 


I. — The  Hypothesis  of  Welch. 

What  has  come  to  be  known  as  the  hypothesis  of  Welch 
is  of  such  practical  and  theoretical  importance  that  ref- 
erence to  it  should  not  be  passed  over.  It  may  be  put 
in  the  form  of  the  following  question:  If  bacterial  tox- 
ins and  the  constituents  of  bacterial  cells  so  act  on  the 
tissue  cells  that  the  latter  produce  bodies  (antibodies) 
Avhich  are  inimical  to  the  bacteria,  why  may  not  the 
body  fluids  in  turn  so  act  on  the  bacteria  that  the  latter 
produce  bodies  (antibodies)  which  are  inimical  to  the 
tissue  cells?  "Looked  at  from  the  point  of  view  of  the 
bacterium,  as  well  as  from  that  of  the  animal  host,  ac- 
cording to  the  hypothesis  advanced,  the  struggle  be- 
tween the  bacteria  and  the  body  cells  in  infections  may 
be  conceived  as  an  immimizing  contest  in  which  each 
participant  is  stimulated  by  its  opponent  to  the  produc- 
tion of  cytotoxins  hostile  to  the  other,  and  thereby  en- 
deavors to  make  itself  immune  against  its  antagonist." 
(Welch.) 

A  more  reasonable  hypothesis  could  hardly  be  ad- 
vanced, and  no  small  number  of  facts  known  at  the  pres- 
ent time  are  in  harmony  with  it.  Walker  had  already 
performed  Avork  of  a  fundamental  character,  which 
showed  that  the  typhoid  bacillus,  when  grown  in  the 
presence  of  its  antiserum,  acquires  greater  virulence  for 
animals.  Furthermore,  a  greater  dose  of  protective 
serum  was  required  to  save  guinea-pigs  from  infection 
with  the  immunized  culture  than  from  the  same  strain 
which  had  not  been  immunized.  The  fact  has  been  known 
for  a  long  time  that  the  typhoid  bacillus  resists  agglu- 
tination when  freshly  cultivated  from  a  patient  ha^nng 
the  disease,  whereas  it  becomes  easily  agglutinable  after 
a  period  of  artificial  cultivation.  It  may  well  be  assumed 
that  the  bacillus,  when  playing  the  part  of  an  infecting 
organism,  gradually  was  immunized  against  the  agglu- 
tinating properties  of  the  patient's  serum;   and,  on  the 


5GS  Al'J'EXDfX. 

otlier  hand,  that  it  lost  tiiis  resistance  after  it  had  been 
removed  from  the  stinuihiting  influence  of  the  infected 
body.  This  immunization  with  agglutinins  may  be  car- 
ried on  in  the  test  glass,  and  bacteria  which  have  been 
so  treated  acquire  the  power  to  absorb  a  greater  quantity 
of  agglutinin  from  the  homologous  serum    (Bail). 

Another  pertinent  observation  w\as  that  by  Wechsberg, 
who  found  that  a  strain  of  the  diphtheria  bacillus  when 
grown  in  a  medium  containing  diphtheria  ant  itoxin 
could  ue  made  to  produce  diphtheria  toxin  more  abund- 
antly. We  may  assume  that  the  antitoxin  combined  with 
the  corresponding  receptors  situated  in  the  bacilli 
(diphtheria  toxin),  and  that  the  bacilli  were,  as  a  result, 
stimulated  to  produce  a  greater  number  of  such  recep- 
tors (toxin). 

Consistent  as  these  observations  are  with  the  hypo- 
thesis under  discussion,  Welch  meant  a  great  deal  more 
than  the  immunization  of  the  bacteria  against  the  de- 
fensive powers  of  the  animal  body.  Not  only  may  a  bac- 
terium during  infection  become  more  resistant  to  the 
bactericidal  action  of  the  body  by  producing  antibodies 
for  those  bactericidal  agencies,  or  by  its  ability  to  ab- 
sorb and  dispose  of  a  greater  quantity  of  bacteriolysin ; 
and  not  only  may  a  bacterium  be  able  to  respond  to  the 
presence  of  natural  antitoxins  in  the  body  by  the  pro- 
duction of  more  toxin;  but,  in  addition,  certain  constitu- 
ents of  our  body  fluids  may,  by  combining  with  suitable 
bacterial  receptors,  stimulate  the  bacterium  to  the  pro- 
duction of  a  Avhole  shower  of  cytotoxins,  which  attack  the 
leucocytes,  erythrocytes,  nerve  cells,  liver,  kidney,  etc. 
The  nature  of  the  animal  substances  which  may  combine 
with  the  bacterial  receptors  and  thus  cause  the  formation 
of  the  bacteriogenic  cytotoxins  is  left  an  open  question, 
and  is  not  of  essential  importance  for  the  theory :  it  is 
not  at  all  necessary  that  they  be  toxic  for  the  bacterium, 
and  they  may  even  be  taken  up  as  food  substances. 
Likewise  the  possible  nature  of  the  cytotoxins  produced 
bv  the  bacterium  is  of  secondary  importance.  It  so  hap- 
pened that  Welch  assumed  that  they  might  be  of  the 
nature  of  amboceptors,  which  may  become  complemented 
by  bacterial  complement,  by  the  circulating  comple- 
ment of  the  body  or  by  endocomplements  of  the  tissue 
cells.     One  could  with  equal  reasonableness  assume  that 


Ar/'ENDfX.  .509 

they  may  be  complete  toxins,  receptors  of  the  second 
order,  with  a  haptophorous  and  a  toxophorous  structure. 

A  well-known  statement  of  Metchnikoff  is  to  the  effect 
that  a  particular  bacterium  when  virulent  is  not  so 
readily  taken  up  by  leucocytes  as  is  an  avirulent  strain, 
'ihis  fact  has  been  noted  repeatedly  in  recent  times  in 
tne  study  of  phagocytosis  in  the  test  tube.  This  may  be 
because  the  organism,  in  its  virulent  parasitic  state, 
secretes  substances  which  repel  the  phagocytes,  neu- 
tralize the  opsonins,  or  because  of  the  formation  of 
actual  leucocytic  toxins. 

One  of  the  most  widely  known  phenomena  in  relation 
to  the  virulence  of  some  organisms  is  that  their  patho- 
genicity may  be  increased  by  passing  them  through  suit- 
able animals  repeatedly.  The  best  results  are  obtained 
when  intermediate  artificial  cultivation  is  avoided  and 
the  inoculations  are  made  directly  from  the  dead  into 
the  living  animal.  It  may,  with  all  reason,  be  assumed 
that  by  continued  residence  in  the  host  the  bacterium 
has  been  trained  to  produce  a  greater  quantity  of  toxic 
substances  which  are  inimical  to  the  host,  and  that  the 
increased  virulence  of  the  parasite  depends  on  this  con- 
dition. 

Although  up  to  the  present  time  systematic  attempts 
to  place  the  hypothesis  of  Welch  on  a  firm  experimental 
basis  appear  not  to  have  been  made,  the  observations 
cited,  as  well  as  others  which  could  be  enumerated,  pro- 
vide cumulative  evidence  of  its  correctness. 

II. — The  Aggressins  of  Bail. 

Not  entirely  foreign  to  the  subject  discussed  above  is 
the  so-called  aggressin  theory  of  Bail,  the  essential  points 
of  which  may  be  given  without  entering  into  a  detailed 
discussion. 

Bail  attributes  to  pathogenic  bacteria  the  property  of 
"aggressiveness,"  through  which  they  directly  antagonize 
the  protective  agencies  of  the  body.  The  micro-organ- 
isms of  highest  parasitic  powers,  the  "true  parasites," 
as  those  belonging  to  the  hemorrhagic  septicemia  group, 
possess  the  greatest  aggressiveness,  since  they  are  able  to 
proliferate  in  the  blood  stream  while  the  antibacterial 
activities  of  the  body  (phagocytosis,  etc.)  are  held  in 
abeyance.     Other  bacteria.  Avhich  in  causing  disease  tend 


.-)70  AITESDIX. 

to  remain  localized,  and,  if  by  any  means  they  reach  the 
blood  stream,  are  not  able  to  proliferate  greatly  in  this 
place,  are  "half  parasites"  and  have  a  lower  degree  of 
aggressiveness;  they  are  more  siisce])tible  to  ))hagocyto- 
sis  and  to  the  action  of  bacteriolysins  (typhoid,  cholera, 
dysentery ) .     [Saprophytes  have  no  aggressive  action. 

This  is  very  general,  but  Bail  and  liis  co-workers  have 
attempted  to  put  the  conception  on  an  experimental  basis 
by  demonstrating  the  existence  of  a  substance  on  which 
i..e  aggressiveness  of  bacteria  depends;  to  this  substance 
tney  give  the  name  of  "aggressin.' 

Intraperitoneal  inoculation  of  the  tubercle  bacillus 
into  the  guinea-pig  leads  to  more  or  less  general  tuber- 
culosis and  to  the  death  of  the  animal  in  the  course  of  a 
few  weeks.  If,  during  the  course  of  the  disease,  a  second 
injection  of  a  large  quantity  of  the  bacillus  is  made  into 
the  peritoneal  cavity,  or  if  an  injection  of  tuberculin  is 
given,  the  animal  dies  very  quickly.  This  is,  of  course, 
nothing  more  than  the  well-known  hypersusceptibility  of 
tuberculous  animals  to  the  products  of  the  tubercle 
bacillus.  In  addition  to  this  fact,  however,  a  similar 
result  was  obtained  in  another  manner.  If  a  large  quan- 
tity of  bacilli  is  placed  in  the  peritoneal  cavity  of  a 
liealthy  guinea-pig,  and  the  exudate  is  removed  after 
twenty-four  hours  and  freed  from  leucocytes  and  bacilli, 
the  aggressin  of  the  bacillus  is  said  to  be  present  in  the 
clear  lluid.  This  is  demonstrated  by  injecting  some  of 
the  iluid,  together  with  tubercle  bacilli,  into  the  peri- 
toneal cavity  of  another  healthy  guinea-pig.  The  rapid 
death  of  the  animal  is  the  result,  whereas  the  bacilli 
alone  cause  death  only  after  a  long  period,  and  the  cell- 
free  exudate  alone  is  without  toxicity. 

A  similar  condition  has  been  found  in  experimental  in- 
fections with  a  number  of  bacteria  (typhoid,  cholera, 
dysentery,  plague,  chicken  cholera),  the  essential  fact 
being  the  same:  that,  following  intraperitoneal  or  intra- 
pleural inoculation,  the  resulting  exudate,  when  freed 
from  leucocytes  and  bacteria,  has  the  power  of  intensify- 
ing an  infection  by  the  corresponding  organism. 

There  seems  at  present  to  be  no  definite  knowledge 
concerning  the  nature  of  these  aggressins.  although  Bail 
thinks  they  may  resemble  true  toxins  in  some  respects. 
Likewise   the    precise    character    of   their    action    is    un- 


APPENDIX.  571 

known,  altlioiigli  Bail  and  liis  ('(j-woikcr.s  are  strongly 
inclined  to  the  view  that  they  inhibit  phagocytosis  by 
some  direct  action  of  the  leucocytes. 

It  is  further  interesting  that  immunization  with  ag- 
gressins  is  said  to  give  rise  to  the  formation  of  anti- 
aggressins,  and  that  by  the  use  of  antiaggressive  serum 
the  action  of  the  aggressins  is  neutralized,  and  the  bac- 
teria consequently  become  the  prey  of  the  leucocytes. 
The  action  of  the  antiaggressive  serum  is  said  not  to 
depend  on  the  presence  of  bacteriolysins. 

One  can  hardly  attempt  a  serious  criticism  of  the 
aggressin  theory  at  this  time,  and  the  above  statements 
are  made  only  to  signify  its  general  character. 

III. — COBBA-LECITHID. 

Too  late  to  be  incorporated  in  its  proper  place  in  the 
text,  it  is  learned  that  the  chemical  identity  and  mole- 
cular weight  of  cobra-lecithid  have  been  determined  by 
Dr.  Kyes  in  the  laboratory  of  Ehrlich,  and  that  work 
descriptive  of  the  characteristics  of  the  substance  is  in 
process  of  publication. 


"BIBLIOGRAPHY:' 


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lihrlich  (and  his  lHlI>il^^•  :  Collecicd  Studies  on  Immunity. 
Autlioiized  Translation  by  diaries  Bolduan,  M.  D.  (Ju  prep- 
araiion).      .lolin    WiU-.v    iJt    Sons,    New    Yoii<. 

Metclinii;oir :  Immunity  in  Infectiye  Diseases,  Masson  et 
C'ie..  Taris,  1!)01.  Translated  by  Binuie.  MacMlllan  &  Co. 
$r>.L'5    net. 

!»ieudonne:  Inununitiit,  Scliutzimpfung  nnd  Serumtlierapy. 
4tli  Edition.  .Toll.  Ambr.  Bartb,  Leipzig,  1905.  (Gives  the 
fundamental  literature.) 

Roger  :  Les  Maladies  Infectieuses.  Masson  et  Cie..  Paris, 
1002.  (Detailed  treatise  on  the  infectious  properties  of 
different    micro-organisms.) 

Kolle  and  Wassermann :  Handbuch  der  I'athogenen  Mi- 
kro-organisiiaen,  Giistav  Fischer,  Jena,  1902-1904.  Kour 
volumes. 

Ritchie  :  Current  Theories  of  Immunity.  Journal  of  Hy- 
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et    Cie..    Taris.    189S. 

Bosanquet :  Serums,  Vaccines  and  Toxins.  Keener  &  Co., 
Chicago.  1904.     :i44  pages. 

Oppenheimer,  Carl  :  Toxine  und  Antitoxine,  Fischer,  Jena, 
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Bensaude :  Le  Ph^nom^ne  de  I'Agglutination  des  Mi- 
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V.   Dungern  :   Die   Antikfirper.      Fischer,   Jena.   1903. 

Wcigert.  E.  :  Les  Tuberculiues.  Storck  et  Clc.,  Lyon, 
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*  Si->e  nolo   in   tlio   Profnce  concerning  Bibliography. 


INDEX, 


PAGE. 

Abrin    0,    104,    204 

Achalme,    bacillus   of,   in    rheumatic   fever    359 

Acne,    staphylococcus    in    370 

Acquired  Immunity    (see  Immunity,  acquired). 
Active  immunity   (see  Immunity,  active). 

Actinomyces  iovis   et  hoininis    (ray   fungus) 10,   458 

Classification  of,  459,  460  ;  cultivation  and  morphology 
of,  459 ;  lungs,  in,  337  ;  occurrence  of,  in  nature, 
460  ;  phagocystosis  of,  461  ;  resistance  of,  459 ; 
species  of,  and  virulence  of,  460. 

Actinomycosis    10,    450-462 

Animals,  susceptibility  of,  to,  460 ;  connective  tissue, 
formation  of,  in,  5,  45S,  461  ;  immunity  and  sus- 
ceptibility to,  461,  462  ;  infection  atria,  460  ;  iodld 
of  potassium  In  treatment  of,  462  ;  lesions,  charac- 
ter of,  45S,  460  ;  phagocytosis  In,  461  ;  prophylaxis 
of,  461  ;  transmission  of,  460. 
Acute  articular   rheumatism    (see   Rheumatic  fever)  ....    541 

Adrenal   gland,   cytotoxln  for .    173 

Agglutination    92,    118 

Of  erythrocytes,  103  ;  of  erythrocytes  with  silicic  acid, 
129 ;  etiology,  determined  by.  7  ;  group  agglutina- 
tion, 110,  113 ;  immunity,  relation  to,  96,  97 , 
macroscopic  and  microscopic,  102 ;  prognostic  im- 
portance of,  95  ;  sodium  chlorld,  influence  on,  110  ; 
stages  in  the  reaction,  110 ;  substances  concerned, 
105  ;  serum  dilutions,  113  ;  specificity.  111  ;  technlc, 
98;  theories  of  mechanism  of,  116;  see  also  under 
Agglutinins  and  under  dlfCerent  diseases  and  micro- 
organisms. 

Agglutinins     92-118 

Absorption  of  by  bacteria,  2u3 ;  agglutinophorous 
group,  108  ;  autoagglutlnlns,  104  ;  chief  agglutinins. 
Ill  :  congenital,  93,  96  ;  definition,  105  ;  distribution 
of,  in  the  body,  95  ;  Ehrllch's  theory  of  the  produc- 
tion of,  114  ;  ferments,  action  of,  on,  96,  107  ;  for- 
mation of,  following  vaccination,  233  ;  haptophorous 
group  of,  108  ;  Hauptagglutinin,  111  ;  immune,  62, 
93  ;  Isoagglutinins,  104  ;  mixed  infections.  Influence  of, 
on,  113  ;  Mitagglutinin,  109  ;  normal,  55,  92  ;  origin 
of,  96  ;  precipitation  of,  by  chemicals,  107  ;  produc- 
tion of.  93  :  receptors  of  2d  order,  108  ;  resistance 
to  acids  and  alkalies,  109  ;  resistance  to  heat,  97, 
108,  109  ;  somatic  and  flagellar,  107  ;  specificity  of. 
92  ;  structure  of,  108  ;  union  with  cells,  character 
of,  203,  204  ;  unit  of  measure  of,  103  ;  variations 
of,  in  animals,  114  ;  variations  in  the  quantity  of, 
95 ;  ^ymotoxic  group  of,  108 ;  see  Agglutination, 
Agglutinogens,  Agglutinoids,  and  also  under  the  dif- 
ferent   micro-organisms. 


574  INDEX. 

}'AG1'.. 

AKiiluiliiosenlc    power    of    bacteria 04 

AgKlutino-iens.  or  asfilutiuable  substances    10r> 

Diffiisibility  of,  1M7  ;  distribution  of,  lUG ;  flagellar 
and  somatic.  loT  ;  nuiltipllcity  of,  107  ;  resistance  of, 
to  heat,  107  :  structure  of,  108 ;  see  Agglutinins 
and  Asrshitination. 

Agglutinoids     109 

Aggressins   509 

Alexins    411,    130 

Delinition  of.   40;   identity  of,   with  complement,   134, 
13r( :  nature  and  selective  action  of,  131 ;  see  Com- 
plement. 
Alkaloids. 

Failure  to  cause  formation  of  antibodies,  198;  state 
of.   within  the  cells,   198,   205. 

Amboceptold •  •    209 

Amboceptors    134,   141 

Absorption  of,  by  cells,  144.  140.  203 ;  bacteriolytic, 
143  ;  complementophllous  haptophore  of,  147  ;  cyto- 
philous  haptophore  of,  14G  ;  formation  of,  150  ;  for- 
mation following  vaccination,  233  ;  hemolytic,  141  ; 
influence  in  phagocytosis.  190 ;  Isolation  of,  14G ; 
manner  of  action  of,  with  complement,  145.  148,  207, 
208  ;  occurrence  of.  In  animal  secretions.  158  ;  origin 
from  leucocytes,  183,  190;  origin  in  cholera,  190; 
receptors  of  the  3d  order,  207  ;  sensitization  by,  142. 
145 ;  solutions  of,  144 ;  specificity  of,  152,  153 ; 
structure  of,  147 ;  svnonvms  for,  148.  217 ;  union 
with  cells,  nature  of,"  147.  148,  203.  204;  see  Hem- 
olysins (serum),  Bacterlolyslns,  Cytotoxins  and 
Venoms. 
Ameba  coli. 

Discovery  of.  502  :  pathogenicity  of.  502  ;  symbiosis  of. 

502  ;   see  Amebic   dysentery. 

Ameba   proteus    500 

Ameba. 

Cultivation  and  distribution  of,  501 ;  phagocytic  action 
of.  170;  resistance  of,  501;  symbiosis,  501,  502. 

Amebic   dysentery    500 

Anatomic  changes  in,  503 ;  immunity  to,  504 ;  liver 
abscess    in,    503 ;    occurrence    of.    502 ;    prophylaxis, 

503  ;  see  Amebns,  and  Ameba  coll. 

Amlbodiastase    176 

Amyloid  degeneration,  production  of  by  staphylococcus.  .    375 
"Anatomic     tubercle"     (see    Tuberculosis  j. 
Animals,    susceptibility    of,    to 

Actinomycosis.   460;   anthrax,   330,  331;   B.  influenza, 

304;  ji.  melUensis,  335;  cholera,  309;  hydrophobia. 

513,    514  ;    leprosy,    447 ;    Micrococcus    catarrhaUn, 

384  ;    Micrococcus    meninc/itidis.    390  ;    oidiomycosis. 

4ii7  ;    pneuraococcus.    339  ;    pseudotuberculosis,    444  ; 

relapsing    fever,     404 ;     staphylococcus.     375.     376 ; 

streptococcus.    352 ;    syphilis.    522 ;    trypanosomiasis, 

490,  495:  tuberculin,  414;  tuberoilosis,  427.  441. 

Animal  experiments,  in  testing  value  of  serums 201 

Anopheles   mosnnitoes. 

A.    inaciiUpennis,   478;    A.    punctipennis,   478;    habits 

of.    478 ;    life   cycle   of.   478.    479  ;    malaria,    rule    in. 

468  ;   migration   of,   479 ;   occurrence,   478. 


INDEX.  575 

PAGE. 

Antliracase-ImmiinpvnteUlin ',',?,2 

Anthrax    32T-;i:i3 

Animals,  Immunity  and  susceptibility  of,  330,  331  ; 
bacillemia,  330 ;  discovery  of  its  microbic  nature, 
27,  28,  29 ;  immunity,  332 ;  immunization,  mixed, 
333  ;  influence  of  streptococcus  on,  362  ;  malignant 
pustule,  329  ;  occurrence,  327  ;  opsonins,  331,  333  ; 
phagocytosis  in,  190,  331  ;  prophylaxis,  330  ;  serum- 
therapy,  332  ;  toxic  results,  330  ;  transmission,  329  ; 
vaccination,  28,  29,  332  ;  wool-sorters'  disease,  329  ; 
see  also  B.  anthracis. 

Antiabrin    90 

Antiaggressins    571 

Antiamboceptors    150 

Danger  in  formation  of,  157  ;  as  receptors  of  the  lirst 
order,  207. 

Antibacterial  serums   (see  Bacteriolysins) 22G-231 

Antibodies. 

Mechanism  of  production,  199 ;  origin  of,  210,  314 ; 
scheme  of,  216 ;  specificity  of,  208 ;  union  with 
antigens,  200 ;  see  Antitoxins,  Amboceptors,  Ag- 
glutinins, Precipitins,  Hemolysins,  Bacteriolysins  and 
C'ytotoxins. 

Anticomplements   154,  207 

Anticrotin     90 

A.ncicytotosins    165 

Antiferments G3,    90 

Antigens. 

Scheme  of,  216 ;  union  with  tissue  cells,  character 
of,    200. 

Antiglobulin    124 

Anti-immune    serum    156 

Antilaccase     90 

Antile\icocidin     90,    372 

Antileucotoxic   serum    169 

Antinephrotoxin    170 

Antineurotoxin     171 

P^or  venom,   266. 

Antipepsin     • 90 

Antiprecipitins     123 

Antirennet    90 

Antiricin    90,   201.  202 

Antirobin    90 

Antispermotoxin    166 

AntJstaphylolysin    380 

Antisteapsin    90 

Antistreptocolysin    353 

Antitoxins    65,   91.    221,   235 

Early  administration  of,  223,  224  ;  curative  action  of, 
222,  223  ;  discovery  of,  33  ;  examination  of  by  U.  S. 
Hygienic  Laboratory,  76 ;  for  animal  toxins,  90 ; 
for  B.  botuHnus,  359  ;  for  B.  diphtheriw,  241.  243  ; 
for  B.  pyocyaneus,  260,  261  ;  for  B.  ietani,  223, 
252  ;  for  bacterial  toxins,  89,  90 ;  for  plant  toxins 
(abrin,  crotin,  ricin,  robin,  phallin),  90,  264:  for 
pollen  toxin,  263  ;  for  zootoxins,  268  ;  formation  of. 
85 :  haptophorous  group  of,  79 ;  infections  charac- 
terized   by    the    formation    of,    235,    268  ;    leucocytic 


:)7(i  i\ni:x. 

I'AGK. 

origin,  question  ol',  191  ;  niauul"acture  ol',  O'J  ;  mode 
of  action  of,  I'Ol,  221,  220;  nature  of,  lUl  ;  toxins, 
neutralization  of,  by,  78,  201,  2U3  ;  normal,  45  ;  pres- 
ervation of,  71,  73  ;  propliylactic  action  of,  226 ; 
receptors,  free,  S9  ;  receptors  of  tlie  lirst  order,  207  : 
relation  of,  to  toxins.  In  tlie  body,  222  :  rela- 
tion of,  to  toxins,  in  vitro,  221  ;  standardization  of, 
72,  25.") ;  unit  of,  72  ;  see  Part  II,  Group  1,  and  also 
tlic  dill'erent  micro-organisms. 

Antitrypsin     90 

Antiurease     ''" 

Antivenin    70,  90,  207,  208 

Aniilyrosinase    90 

Arachnolysin    (spider    poison)     10,    268 

Arrhenius    and    Madsen,    views    of    210 

Anltritis    344,   348,   354,   378,   386,    391 

Asperj;illus     6.    407 

Atropliy,  phagocytosis  in    178,  179 

Attenuation. 

Importance'  of   in  vaccination,   57  ;   methods  of,    219. 

Autougi,'lutinins    104 

.A.ulocytotoxins    103,    174 

Autolytic    products,    vaccination   witli    220,   312 

.^.uiouephrotoxins     169 

Autoprecipitins     121 

Autospermotoxin 160 

Bucillus  ii'drogenes  capsulatun   14,  185,  359 

liaLillus    alcaligencs    270 

IJfiilliis  aiithracis 10,  327-329 

Antagonism  of,  bv  other  bacteria,  329  ;  antiserums  for, 
32^;  attenuation  of,  58,  219 ;  cultivation  of,  328 ; 
discovery  of,  27,  327  ;  gastric  juice,  effect  of,  on,  39, 
329 ;  iicmunity,  active,  332 ;  immunity,  acquired, 
186,  331  ;  immunity,  natural,  330 ;  immunity, 
passive,  332  ;  infection  atria,  39 ;  opsonins,  331  : 
phagocytosis  of,  331  ;  serums,  effect  of,  on,  48,  49, 
331 ;  spores  of,  29,  327,  328 ;  toxic  properties  of, 
330  ;  vii-ulence  of,  329 ;   see  Anthrax. 

Bacillus   botulinus    250,    257 

Animals,  susceptibility  of,  257,  258 ;  antitoxin  for, 
259  ;  morphology,  etc.,  257 ;  occurrence  in  meat, 
257  ;  saprophytic  nature  of,  258 ;  spores  of,  257  ; 
toxin,  action  of,  258  :  toxin,  detection  of  in  meat, 
257  ;  toxin,  preparation  and  resistance  of,  258 ; 
see  Botulism. 
Bacillus    chanori    mollis    (bacillus    of    Ducrcy  ;    bacillus 

of   soft   chancre)     , 10.    399 

Cultivation,  morphology,  phagocytosis  of,  susceptibil- 
ity  of   animals   to,   400. 

Bacillus   of   chicken    cholera    58 

Bacillus    coli    cominunis    298-304 

Agglutination  of,  92,  94.  Ill,  304  ;  autagoni.sm  for  pu- 
trefactive bacteria,  299,  300  ;  antiserums,  properties 
of,  303  ;  beneficial  functions  of,  299  ;  in  cystitis,  303  : 
in  enteritis,  40,  301,  303;  group  agglutination.  111; 
group  of,  298  ;  in  meningitis,  389  ;  morphology  and 
staining  of,  298;  occurrence  in  intestines,  298,  299; 
occurrence   in   nature.   29S  ;   in   pneunionin.   330:    ro- 


INDEX.  577 

PAGE. 

sistance  of,  208,  290  ;  serums,  effect  of,  on,  200  ;  sym- 
biosis with  Amelta  coli,  502  ;  toxin  of,  303  ;  typicai 
strains   of,    290;   virulence  of,    300,   301,    302. 

Bacillus   diplitheriw    10,    235,    236 

Agglutination  of,  243 ;  antitoxin  for,  89,  241,  242 ; 
morphology,  staining,  cultivation,  resistance,  viabil- 
ity of,  236 ;  occurrence  of,  in  the  body,  237,  238  ; 
phagocytosis  of,  240  ;  pneumonia,  in,  33G  ;  toxic  ac- 
tion of,  15  :  toxins  of,  66,  67,  237,  238,  242  ;  toxin, 
attenuation  of,  40,  210 ;  tuberculosis,  in,  425 ; 
see    Diphtheria. 

Bacillus   of   Ducrey.      See  Bacillus   chancri  mollis. 

Bacillus    dysenteriw    10,    288-290 

-Agglutination  of,  92,  94,  288,  289,  294 ;  antiserums 
for,  properties  of,  293  ;  cultivation  and  morphology 
of,  288,  280 ;  dissemination  of,  292 ;  endotoxin  of, 
291  ;  etiologic  role  of,  280  ;  "Flexner"  type  of,  289  ; 
pseudodysentery  bacilli,  288  ;  toxicity  of,  291 ;  toxin, 
autolytic,  of,  201  ;  types  of,  288 ;  see  Dysentery, 
acute    epidemic. 

Bacillus  edemor,  maligna)   1,  14 

Bacillus    enteritidis    294-298 

Agglutinins  and  agglutination  of,  94,  298 ;  Bacillus 
paratypliosus ,  resemblance  to,  285 ;  discovery  of, 
295 ;  fermenting  powers  of,  295  ;  group  agglutina- 
tion, 111  ;  group  of,  295 ;  meat  poisoning  by, 
294-208 ;  morphology  and  staining  of,  295 ;  occur- 
rence of,  in  meat  of  horses  and  cattle,  295,  296, 
297  ;  poisoning  by  oysters  and  fish,  in,  297  ;  resist- 
ance of,  297  ;  toxin,  295-206  ;  toxin,  occurrence  in  , 
meat,    297 ;    toxin,    resistance   of,   297. 

Bacillus    of    Friedlander ;    see    Bacillus    pneumonice. 

Bacilli    from   butter,    grass   and   milk    444 

Bacillus  icteroides,   in   yellow  fever 11,    530,   531 

Bacillus  influenzos 10,  394 

Agglutination  of,  399 ;  animals,  virulence  for,  395 ;' 
antiserum,  properties  of,  390 ;  in  conjunctivitis. 
396  ;  cultivation  of,  394  ;  discovery  of,  394  ;  excre- 
tion of,  395 ;  hemophilic  properties  of,  394 ;  im- 
munization with,  399 ;  in  meningitis,  389-306 ; 
morphology  and  staining  of,  394  ;  occurrence  of.  in 
the'  body.  396  ;  otitis  media,  in,  396  ;  peritonitis,  in, 
396 ;  resistance  of,  395 ;  symbiosis  of,  394 ;  toxin 
of,    395  ;    tuberculosis,    in,    425  ;    see  '  Influenza. 

Bacillus   lactis   aerogenes. 

Antagonistic  action  on  putrefactive  bacteria,  300  ;  oc- 
currence in   intestines,  401. 

Bacillus    lepras 10,    446 

Animals,  insusceptibility  of,  to,  447  ;  antiserums  for, 
452  ;  discovery  of,  446  ;  endotoxin,  question  of,  450  ; 
excretion  and  occurrence  in  nature  of.  447  ;  incul- 
tivability  of,  447  ;  morphology  of,  447  ;  occurrence 
in  the  body,  449 ;  phagocytosis  of,  449,  451  ;  see 
Leprosy. 

Bacillus    of   Lustgarten 443,    552 

Bacillus    mallei     10,     453 

Agglutination  of,  458  ;  cultivation,  morphology  and 
resistance  of,    453  ;   mallein,  varieties,   and  prepara- 


57S  IXDEX. 

PAGE. 

lion   ol",    4."(4  ;    im'iiiii.uilis.    in,   :1^'.' ;    i)ha,:j;oc.vtosis  of, 
4riG, 

Bacitliis  melitensis    334,   335 

AgTfil'itination  of.  o34 ;  animals,  siisceiilibility  of,  to, 
3;>o  ;  morphology  of,  334  :  opsonins,  iulhieuce  of  In 
phagocytosis  of,  .  334  ;  serums,  effect  of,  on,  334; 
see  Malta  fever. 

Ba<  illiis  inucosus  vupsulutiis   401 

Bacillus  of  ozena 402 

BaciUus  vai-'ityphosus 284 

Agglutination  of,  11,  2S4,  287 ;  antiserums  for.  jm-oi)- 
erties  of,  287  ;  blood  cultures,  288  ;  endotoxin,  287  ; 
excretion  of,  28G ;  meat  poisoning  by,  285 ;  occur- 
rence in  the  body.  280 ;  "paracolon"  bacilli,  rela- 
tion to,  285 ;  resistance  of,  280 ;  toxicity,  287 ; 
tvpes   of.    285 ;    see   Paratyphoid   fever. 

Bacillus  pestis    10,  316-319 

Agglutination   of,    94,    320 ;    cultivation   of,    310,    317 ; 
endotoxin,    resistance    of,    319 ;    excretion    of.    321  ; 
involution    forms.    317 ;    meningitis,    in,    389 :    mor- 
phology,  310;    phagocytosis   of,   325;    pleomorphism, 
316 ;    pneumonia,   in,   330 ;    resistance   and   viability, 
317,   318  ;   staining  of,   310 ;   toxicity  of  cell   bodies, 
310 ;    toxiu    of    Lustig    and    Galeotti,    318 ;     toxin, 
soluble,     question    of,     318 ;     virulence,     318,     319 ; 
see    I'lague. 
Bacillus  pneumonia-  (bacillus  of  Friedlander)  .    337,  401,  402 
Agglutination  of,   94,  402  ;   antagonism  for  B.  anthra- 
cii?,    329 ;    antiserum.    402 ;    influenza,    397 ;    lesions 
caused  bv,  402  ;  meningitis,  in,  389  ;  pneumonia,  in, 
336,  344.'  402  ;  tuberculosis,  in,  425. 
BaciUus    proditJiosus. 

Antagonism  for  B.  anthracis,  329;  Coley"s  mixture,  in, 
362 ;    symbiotic  action   of.    185. 

BaciUus  psittacosis,  agglutination  of 94,  111 

Bacillus    pseudotuberculosis,    varieties    of    445 

Bacillus    pyocyaneus    259-261 

Agglutination  of,  92,  94 ;  agglutinins  for,  261 ;  agonal 
invasion  by,  259  ;  antagonism  for  B.  anthracis,  329  ; 
antitoxin,  261  ;  bactericidal  serum  for,  261  ;  fer- 
ments of,  260  ;  endocarditis,  in.  259  ;  endotoxin  of, 
260 ;  enteritis,  in,  40 ;  infections,  symptoms  of. 
260 ;  meningitis,  in,  259 ;  pigments  of.  200 ;  pyo- 
cyanase.  260  ;  pyoc.vanolysin.  260  ;  p.vocyanin,  360  ; 
secondary  infections  by,  259 ;  septicemia,  in.  259 ; 
toxic  action  of,  16  ;  toxin,  soluble,  06,  260,  261  ;  tu- 
berculois.   in,  425. 

Bacillns     of     rhinoscleroma     402 

Bacillus    of    symptomatic    anthrax    185 

Bacillus    tetam     244-256 

Agglutination.  256:  anaerobic  property  of,  247;  ani- 
mals, susceptibility  of,  to  toxin,  51  ;  avirulent 
strains,  249  ;  discover.v  of,  244  ;  morpholog.v,  stain- 
ing, cultivation,  244.  245  ;  occurrence  in  intestines. 
246;  occurrence  in  nature.  245;  parasitic  power  of, 
247:  pnthogenlc  properties  of.  249;  resistance  of 
spores  of.  246  :  toxins  of.  15.  20.  00,  07,  249  ;  toxin, 
absorption  of.  by  leucocytes.   191:  toxin,  fixation  of. 


INDEX.  579 

PAGF 

by  tissues,  52,  ij.'i,  204.  205,  222,  251  ;  toxin, 
attenuation  of,  21!) ;  toxin,  action  of  gastric  .juice 
on,  ."'.0  ;  toxin,  neutralization  of,  by  antitoxin,  224  ; 
action  of  pancreatic  juice  on,  40 ;  virulence,  185 ; 
see  Tetanus. 

Bacillus    tuberculosis     10,    407 

Agglutination,  438,  440 ;  agglutination,  relation  of 
to  immunity,  97  ;  animals,  susceptibility  of  to,  427  ; 
antiserums,  properties  of,  4.38 ;  attenuation  of, 
410  ;  avian,  442  ;  bacteria  resembling,  443  ;  bovine, 
differentiation  of  bovine,  from  human,  417 ;  con- 
stituents, 411  ;  cultivation,  409 ;  discovery  of, 
407 ;  effect  on  tissues,  42,  44,  422-425 ;  ex- 
cretion of,  414,  415,  419 ;  fever  producing 
s!il)stance  of,  411  ;  of  iish,  443 ;  gastric  juice,  re- 
sistance to,  39.  410  ;  immunization  with,  411,  430- 
432 ;  inflammation  of  lungs,  in,  337  ;  lesions  pro- 
duced by,  411  ;  morphology  of,  408 ;  occurrence  in 
nature,  414 ;  pathogenic  properties  of,  411 ;  pha- 
gocytosis of,  421,  422  ;  proteins  in,  411  ;  resistance 
of,  409 ;  staining  properties  of,  408,  411 ;  strepto- 
coccus, influence  of.  on  cultui'es,  356  ;  "toxalbumin" 
of,  411;  toxic  substances,  effects  of,  411;  toxin  of 
Marmorek,  404 ;  toxins,  439,  440 ;  virulence  of, 
410,    427 ;    see   Tuberculosis. 

Bacillus  tuphosus    10,  269 

Agglutination  of,  92,  94,  116,  283,  284 ;  antitoxin, 
question  of,  271  ;  autolysis  of,  271  ;  blood  cultures 
of,  273,  284 ;  discovery  of,  269 ;  dissemination  of, 
270 ;  endotoxin,  271  ;  excretion  of,  273,  274  ;  ex- 
tracts of,  282  ;  gastric  juice,  action  of,  on,  39  ;  im- 
munization with,  280,  281,  283  ;  leucocytes,  relation 
of,  to,  277  ;  meningitis,  in,  380 ;  morphology  of,  269  ; 
occurrence  in  body,  9,  270,  274  ;  occurrence  in  na- 
ture, 270";  phagocytosis  of,  274  ;  pueumonia,  in,  336  ; 
resistance  of,  270  ;  symbiosis  with  Ameha  coli,  502  ; 
toxin  of  Chantemesse,  282  ;  vaccines,  279,  232 ; 
see    Typhoid    fever. 

Bacillus    xerosis     244 

Bacterium  coli  commune;   see  Bacillus  coli  communis. 

Bactericidal    serum,    substance,    etc. ;    see    Bacteriolysins. 

Bacteriolysins    130 

Absorption  of.  by  bacteria.  136;  composition  of,  134; 
curative  value  of,  227,  231 ;  endotoxins,  action  on, 
136,  228 ;  group  reaction  with,  135 ;  immunity, 
relation  of,  to,  135  ;  inactivation  and  reactivation  of. 
133,  134  ;  nature  and  selective  action  of,  131  ;  ori- 
gin of,  from  body  cells,  45.  138  ;  properties,  general. 
130  ;  prophylactic  value  of,  227  ;  specificity  of,  135  ; 
standardization  of,  138 ;  technic  of  testing.  139 ; 
therapeutic  use  of,  226  ;  see  Amboceptors  and  Com- 
plements. 

Bacteriolysis    and    bacteriolysin     130 

Bacteriolysis. 

Group  reaction.  153;  mechanism  of.  145:  Pfeilfer's 
phenomenon.  131  ;  similarity  to  hemolysis,  134  ; 
see  Bacteriolysins. 

Bacteriolytic   enzymes,    relation    to   immunity    61,    62 


5S0  y.\7>/;.v. 

FAOB. 

Bacteriotropic   substances    227,    346.    309,    381 

Balaiitidiinn     roli,    morphology,    occurrence    and    patho- 
genicity        505,    506 

Balaiitidiiitii,     miniitttm     506 

Keuzol   ring;   use  of,   as  an   analogy   in   ICIirli.-h's   theory 

106. 
Bile. 

Bactericidal   and   antitoxic   propenies   ot,   4ii  ;    iinnnine 
agglutinins    in,    i)'^. 
Biologic    test    Tor    species;    see    I'lecipiiin^. 
"Blacl<  Death"  ;  see  Plague. 

"Blaekwater    fever"    in    malaria     477 

Blastoniycetic  dermatitis ;    see   Oidiomycosis. 
Blastomycosis  ;  see  Oidiomycosis. 

Blue    pus     259 

Bodo     Hfinariiifs     508 

Botulism    10,   250-259 

Absorption  of  toxin,  258  ;  antitoxin,  90,  259  ;  immun- 
ity, 25!) ;  infected  meats,  250,  257 ;  phagocytosis, 
258  ;  prophylaxis,  259 ;  susceptibility,  258 ;  symp- 
toms, 250 :  tissues  affected  by  lo.vin,  258 ;  see 
BaciUii-i     hotKliniis. 

Bovine    pest    11 

Bronchitis. 

In  epidemic  cerebrospinal  meningitis,  391  ;  meningo- 
coccus in,  391  ;  Micrococcus  catarrhulis  in,  384, 
391  ;   staphylococcus  in,   377  ;  streptococcus  in,   354. 

Capsulated     bacilli     401,     402 

('arbuncle,    staphylococcus    in 370,    377 

Carcinoma,    hereditary    susceptibility    to 18 

Cell    receptors ;    see    Receptors. 

Cercomonas    iiilcstiiialis,    morphology    and    pathogenicity 

of    506,    507 

Chancroid ;    see    soft    chancre. 

Chemicals  in   relation   to   antibody    formation.; 198 

Chemotaxis -13,  44,  177,  185 

Chicken   cholera,   attenuation    of   microbe   of    219 

Chicken  pox  (varicella  I    555,  556 

Chicken    typhus    or    chicken-pest    11 

Cholera    10,   304-315 

Accidental,  in  man,  313;  agglutination  reaction,  315; 
animals,  susceptibility  of,  to,  309 ;  anti-bodies, 
origin  of,  190.  314  ;  antitoxic  serum,  315  ;  bacteri- 
cidal power  of  body  fluids,  313  ;  "cholera-carriers," 
304,  313  ;  diagnosis,  bacteriologic.  315 ;  epidemiol- 
ogy, 307.  308,  311,  312;  experimental,  in  man,  313; 
gastric  .inice.  protective  action  of,  313;  geographic 
distribution  of.  307.  308  ;  immunity  and  susceptibil- 
ity to.  50,  00,  190,  313,  314  ;  infection  atrium, 
307 ;  lesions,  intestinal,  310 ;  effect  of  leucotoxic 
scrum  on  Infections,  168 ;  mechanism  of  intoxi- 
cation. 310  :  mixed  immunization  in.  234,  314  ;  phag- 
ocytosis, 188.  189,  313,  314  ;  phagolysls.  188  ;  proph- 
ylaxis, 218,  307,  311  :  serum  properties  in,  20,  97  ; 
serum  therapy,  230.  314.  315  ;  sources  of  infection 
and  transmission.  307-309 ;  vaccines  and  vaccina- 
tion.   58,    312,    313  ;    see   Vibrio   cholera;. 

Cholesterin,    neutralizing   action    on   tetanolysin 91 

Chromophages     179 


ITS/DEX.  581 

PAGE. 

Cladothrix,    infections    witli     463 

Clavelf'e    (slieep-pox)     11,    554 

Co-agglutinins HI 

Cobra-lecitliid   ICO,   200,   .=571 

Col^ra  venom ;   see   Venoms. 

Coccidia,    life    cycle',    morphology,    spore    formation    and 
patbogenicity,   508,   500. 

Coccidiosis     508,    509 

Coccidium    Mgeminum     500 

Coccidium   cuniculi  s.    oviforme    509 

Corodacteria    septica    (Billroth)     349 

Coleys    mi.^tnre     362 

Colle's   law ;    see   Syphilis. 

Colloids 127,  128 

Complement. 

Absorption  of,  145.  229 ;  decrease  of  during  disease, 
280  :  diversion  of,  157,  229,  230  ;  isolation  of,  140  ; 
lecithin  as  a.  160  :  multiplicity  of,  153.  210  ;  origin 
of,  138,  ISO ;  neutralization  of,  by  salts,  91,  161  ; 
receptors  of  second  order,  207  ;  resistance  to  heat, 
184  :  solutions  of.  144  :  sources  of,  for  bactericidal 
serums.  228,  229 ;  specificity  of,  152 ;  structure  of. 
149 ;  unicity,  theory  of.  210 ;  see  Cytase. 
Complemintophilous     haptophore ;     see    Haptophore. 

Compleraentoid    . 149,   209 

Complementnid-'Verstopfung     150 

Conjunctivitis. 

B.  influensce,  in,  396,  397 ;  diphtheritic,  237 ;  menin- 
gococcus in,  391  ;  pneumococcus  in,  348,  349 ; 
staphylococcus    in,    377. 

Connective   tissue,   role  of,    in   innammation 5,   42,   46 

Contact    infection    3 

Contagion   and   contagiousness    2 

Contagious    disease,    definition    2 

Copula    of   Mtiller.    synonyms   for    148 

Cow  pox 550,   554 

Crotin    104.    264 

Cr.vstalloids.    properties    of    127 

Culex  fatigans    540 

Culex  pipiens,  in   transmission  of   malaria   of  birds.  .  .  .    483 

Curative   injections    220 

Cyclasier     scarlatinalis     556 

See    Scarlet   fever. 

Cystomonas    urinariiis     508 

Cytase    178,    181,    182 

See    Complement. 

Cytorifctex  variolm  s.  vctccinw   543 

Conjugation,  544,  545 ;  cytoplasmic  stages,  544 ;  life 
history  of,  54-546 ;  nuclear  stages,  544  ;  smallpox, 
in,   543 :   vaccinia,    in,    545. 

Cytotoxins    (Cytolyslns)     55,    62,    162-175 

Activity,  determination  of,  164  ;  amboceptors  in,  165  ; 
antileuco  toxin,  169;  antinephrotoxm,  170;  anti- 
spermotoxin,  166 ;  autocytotoxins,  163.  174  ;  auto- 
nephrotoxins,  169 ;  autospermotoxin,  166 ;  ciliated 
epithelium,  cytotoxin  for,  167 ;  complements  In, 
165  ;  for  malignant  tumors,  164  ;  hepatotoxins.  171  ; 
infections,  effect  of  leucotoxins  on,   168  ;  leucotoxin, 


oS-2  INDEX. 

PAGE. 

167 ;  nephrotoxin,  169 ;  neurotoxins,  171 ;  origin, 
180;  of  venoms,  2(55,  12GG ;  pancrootoxln,  173; 
specificity,  lack  ot".  IGl' :  sporiuotoxln,  H'>,"> ;  structure 
of,  105;  syncytiotoxiii,  171;  technlc  of  i)roductlon, 
104  ;  thyrotoxin.  17;^  ;  utility,  theoretical,  Hj2,  108. 
Cytolysins  ;    see    Cytotoxins. 

Dacryocystitis,    pucumococcus    in     348 

Daplinla,    phagocytosis  of    183 

Dengue    fever    539,    541 

iharacteristics  of,  546 ;  contagiousness  of,  540,  541  ; 
Culex  fathjaiix  in  transmission  of,  540 ;  etiology, 
540 ;  occurrence.  530 ;  "plasmelja"  in.  540 ;  recur- 
rences and  relapses,  541  ;  suscepiibillty  to,  541  ; 
transmission,    540. 

Desmon    148 

Deuterotoxin    83.    209 

Diphtheria    10.   13.  20,  235-244 

Agglutination  reaction,  243 :  bacilli,  localization  of, 
2;)8 :  conjunctivitis,  diphtheritic,  237 ;  forms  of, 
237  ;  immunity  and  susceptibility,  50,  01,  230,  240  ; 
infection  atria,  237  ;  latent.  237  ;  leucocytes  in,  240  ; 
mixed  infections  in,  14,  238,  186,  358 ;  paralysis, 
influence  of  antitoxin  on.  242  ;  predisposing  causes, 
240 ;  pneumonia  in,  344  ;  prophylaxis,  240,  241  ; 
pseudodiphtherla  bacilli  in.  243  ;  recurrences,  50, 
240  ;  septic,  230  ;  serum  therapy,  225,  241  ;  sources 
of  infection,  236,  237 ;  tissues  Injured  by  toxin, 
23S  :  transmission,  237  ;  vulva,  of,  237  ;  see  Bacillus 
di/jlithcriw. 
Diplococcus  iiitraccllularis  mciiiiif/ilidis ;  see  Micrococcus 
meiiinpitidis. 

Diplococcus  pneumonia;   336-349 

Agglutination  of,  347  ;  alveolar  abscess,  in,  348  ;  ani- 
mals, susceptibility  of,  339 ;  antiserums,  properties 
of,  340 ;  conjunctivitis,  348.  349 ;  dacryocystitis, 
348  ;  discovery  of,  337  ;  endotoxins,  339  ;  enteritis, 
348,  349 ;  group  agglutination,  348 ;  Immunization 
with,  345,  346,  347  ;  influenza,  in,  397  ;  meningitis, 
348,  349,  389 ;  morphology,  staining,  and  cultiva- 
tion, 337,  338 ;  neurotoxic  strains  of,  339 ;  occur- 
rence in  blood.  343 ;  occurrence,  normal,  339 ;  op- 
sonins in  phagocytosis  of,  346 ;  otitis  media,  in, 
348.  349  :  peritonitis,  in.  .348,  349  ;  phagocytosis  of, 
346 ;  pneumonia,  in.  337-348 ;  pneumotoxin,  339, 
346 ;  pulmonary  hemorrhage,  in,  344  ;  resembljince 
to  streptococcus,  338 ;  resistance,  338 ;  rhinitis, 
in,  348;  septicemia.  348;  serpent  ulcer,  348,  340; 
tuberculosis.  In,  425  ;  virulence,  338  ;  virulence,  in- 
crease  of,    342 ;    see   Pneumonia. 

Diplococcus    (streptococcus)    in    rheumatic    fever 359 

Donrine ;    see    Trypanosomiasis    in    animals. 

Droplet    infection     237 

In  diphtheria,  237  ;  in  influenza,  397  ;  in  tuberculosis, 
415. 

Drug    habituation    22 

Dust   infection    237 

In  diphtheria.  237  ;  in  influenza,  3!t7  ;  in  tuberculosis, 
415 ;    in    typhoid    fever,    272. 


INDEX.  583 

PAGE. 

Dvsenterv,   acute  opidemic    8,   10,   288-204 

"Agglutination  reaction,  204 ;  antiserums,  properties 
of,  203 ;  bacilli,  clisseminatlon  of,  by  stools,  292 ; 
bacilli,  distribution  of.  in  the  body,  290 ;  chronic, 
288,  292 ;  immunity  and  susceptibility,  60,  202, 
293:  incubniion  period,  288;  institutions,  occurrence 
in.  202:  iiilcslinal  lesions  in,  200;  occurrence  of, 
288  ;  predisposing  causes  of,  202  ;  prophylaxis,  292  ; 
serum  therapy,  293  ;  summer  diarrheas  of  infants, 
289 ;  transmission,  292 ;  vaccination,  293 ;  see  Ba- 
cillus  (lysentericE. 

Eclampsia,  relation  of  syncytiotoxin  to 171 

Eczema,   relation   of  staphylococcus  to    376,    377 

Eel    serum,    antitoxin    for    90 

Ehrlich's    partial    saturation    method    80,    209 

Ehrlich's    "side-chain"    theory.       See    "Side-chain"     the- 
ory of  Ehrlich. 

Emboli,  bacterial    4 

Endocarditis. 

Colon  bacillus  in,  302  ;  gonorrheal,  386  ;  pneumococcus 
in.   344,  348  ;   staphylococcus   in,  359,   377 ;  strepto- 
coccus   in.    354.    358,    359. 
Encephalitis,    in    epidemic    cerebrospinal    meningitis....    .391 

Endocomplement     159,    266 

Endotheliotoxin,   of   venom    265 

Endotoxins    330 

Anthrax  bacillus,  330  ;  Bacillus  pyocyaneus.  260,  261  ; 
bacteria  containing,  226,  231  ;  cholera  vibrio,  300  ; 
diseases  associated  with,  269 ;  dysentery  bacillus, 
291  ;  failure  of  bactericidal  serums  to  neutralize, 
227 ;  glanders  bacillus.  453 ;  of  gonococcus,  385 ; 
leprosy  bacillus,  450  ;  liberation  of,  by  bacteriolytic 
serums,  136,  228;  meningococcus,  390;  paratyphoid 
bacillus,  287 ;  plague  bacillus,  318 ;  pneumococcus, 
330 ;  staphylococcus,  262,  373 ;  streptococcus,  262. 
353  ;  tubercle  bacillus,  411  ;  typhoid  bacillus,  271. 
Enteritis. 

Amcha  coli  in ;  see  Amebic  dysentery ;  Balantidiiim 
coli  in,  505  ;  Cercomanas  intestinalis  in,  506  ;  colon 
bacillus  in,  303  ;  pneumococcus  in,  348,  349  ;  staph- 
ylococcus in,  377  ;  streptococcus  in,  354,  355,  357  ; 
Trichomonas    intestinalis    in,    507. 

Enzymes,  bacteriolytic,  relation  to  immunity 61,  62 

Enzymes,    intracellular     176 

Epilepsv.    cytotoxin    in     174 

Epithelioma   contagiosum   of   fowls    11 

Epitoxoids     81 

Erysipelas     355 

Effect  on  tumors,  362  ;  experimental  production  of,  by 
streptococcus,  355  ;  in  course  of  tuberculosis,  356  ; 
recurrence  of,  56  ;  staphylococcus  in,  355  ;  strepto- 
cocci   in,    350,    354. 

Etiology,     infectious     7 

Etiology,  unknown    10,   510 

Exhaustion,    toxin   of    174 

Farcin    da    bwuf 463 


584  IXDEX. 

PAGE. 

Farcy,    sec    Glanders     10 

Fermentation,    early   studies   on    27 

Fibrin,   mechanical   value   of   in   inllammation 45 

Fixator,    aynonyms    for    148 

See    Amboceptors. 

Filaria    perstans    487 

Filaiia  sanguinis   hominis    4 

Fish,  B.  cntcfitidis  in  poisonous 297 

Fish  poisons,  antitoxins  for    90 

Fleas,   in  the  transmission  of  plague    ^520,   321 

Flies,   as  carriers  of  tvphoid   fever 272 

Fomites    3,    532,    539 

Food-substances. 

Fixation  of,  by  amboceptors.  208 ;  manner  of  union 
with  cells,  197 ;  non-formation  of  antibodies  for,  109. 

Foot  and  mouth  disease    11,    12 

Fowls,   epithelioma  contasiosum   of    11 

"Gambian    Fever"  ;    see   Trypanosomatic    Fever. 
Gastric    juice. 

Protective   role   of,   39.    313.    329. 

Gelatinase    371 

German    measles    (Rotheln)     562 

Glanders    (Farcy)     10.    30.   452-458 

Agglutination  reaction.  458  ;  animals,  susceptibility  of. 
452 ;  bacilli,  distribution  of,  in  the  body.  454 ; 
connective  tissue  development  in,  456 ;  diagnosis, 
bacteriologic.  457;  healing  processes  in.  456;  im- 
munity, 456 ;  infection  atria,  454.  455 ;  mallein 
in  diagnosis  of,  457 ;  organs  involved,  456 ;  pha- 
gocytosis, 456  ;  serum  therapy,  457  ;  tissue  reactions, 
455 ;  see  RaciUus  mallei. 
GJossina  palpalis  in  transmission  of  sleeping  sickness..  488 
Gonococcus ;    see   Micrococcus   yonorrhea;. 

Gonorrhea    10,   56,   384-388 

Acute  and  chronic,  387.  388 ;  complications  of,  380, 
387  ;  immunity,  56,  387,  388  ;  ophthalmia  in,  386  ; 
phagocytosis,  385,  389 ;  reinfection,  387,  388 ;  su- 
perinfection, 388  ;  susceptibility  of  different  tissues 
to,  386 ;  urethral  changes.  387 ;  see  Micrococcus 
gonorrhea;. 

Gonotoxin     386 

Grass    bacilli    444 

Oregarina  lindemanni ;  see  Sarcosporidia. 

Group  agglutination    110.   113,   284,   287.  298,   348,   369 

Gruber-Widal    reaction ;    see    Agglutination. 

Hairs,    phagocytosis   of   pigment    by    chromophages    ....    179 

Halteridium.  r 

Impregnation  of  parasite,  468  ;  in  malaria  of  birds,  483. 

Haptophores    T9,    197,    199,    207 

Ilaptophorous   groups ;    see    Haptophores. 

llaupiagglutinins     HI 

Hav   fever    262,    263 

Antitoxin    (pollantin).    90,    263;    pollen    as    cause    of, 
262 ;    toxin    of,    262. 
Hanging-drop   preparation    98 


INDEX.  585 

PAGE. 

Hemagglutinins. 

Of  plants,    103  ;   of  serums,   104  ;   of  venom,   2G5. 

Hemoglobinuric    fever,    in    malaria    477 

Hemolysins. 

Animal,  264,  268 ;  bacterial,  202 ;  cobra  lecithld,  160, 
-O'j,  571  ;  colloids  as,  160  ;  e'xperimental  value  of,  141  ; 
from  organ  extracts,  180 ;  immune,  in  serums,  62. 
141  ;  intraleucocytic,  ISO ;  normal,  in  serums,  .'54 ; 
pyocyanolysin,  260  ;  serum  hemolysins,  structure  of, 
141  ;  staphylococcus,  see  Staphylolysin  ;  streptococ- 
cus, see  Streptocolysin ;  tetanolysin,  249 ;  venom, 
of,  265. 
Hemolysis,  see  Hemolysins. 
Hemolytic  experiments. 

Technic  of,   141  ;  value  of,  in  study  of  immunity,    142 

Hemorrhagic    septicemia   group    of    bacteria    .316 

Hemorrhagin    159,  265 

Hemotoxins     67 

Hepatotoxins 171 

Heterologous    serum    94 

Homologous     serum     94 

"Horror    autotoxicus"     174 

Horsepox     554 

Hydrophobia    10,    510-521 

Animals,  in,  51.3,  514  ;  antiserum,  properties  of,  421  ; 
diagnosis,  in  dogs.  515,  516 ;  extension  through 
nerves,  517  ;  fixed  virus  of,  51.3  ;  immunity,  charac- 
ter of,  521  ;  immunization,  mixed,  521  ;  incubation 
period,  514,  515,  517,  518  ;  micro-organisms  found 
in,  510  :  Negri  bodies.  510.  511  ;  Pasteur  treatment, 
518,  52]  :  prophylaxis  of,  517,  521  ;  specific  ( ?)  le- 
sions, 516 :  street  virus  of,  512 ;  transmission  of, 
514:  toxin,  question  of,  511;  vaccination,  29.  30, 
519 :  vaccine,  preparation  of.  518,  519  ;  virulence 
for  man.  513,  517,  520  ;  virulence,  increase  and  de- 
crease of.  by  passage,  513 :  virus,  attenuation  of, 
58.  23  9.  511,  518-520;  virus  de  rue,  513;  virus,  dis- 
tribution and  excretion  of,  518  :  virus,  filterability 
of.  12.  511;  virus  1ixe,  513,  518:  virus,  resistance 
of,    512. 

Ichthyosismus     256 

Ichthyotoxin      268 

Immunitv. 

Absolute.  21  :  acquired,  18,  56-64  :  active.  21.  56.  59  ; 
antibacterial.  19.  47,  48,  49,  211  ;  antitoxic,  19,  49, 
50,  210 ;  definition  of,  17 ;  in  families,  IS ;  leuco- 
cytes, relation  to ;  see  Phagocytosis ;  natural,  18, 
35-55  :  early  theories  of.  24  ;  passive.  21,  60  ;  rela- 
tive, 21  ;  theories  of,  30-34  ;  types  of,  22  ;  see  An- 
titoxins, Bacteriolysins,  Phagocytosis  and  the  indi- 
vidual diseases. 
Immunization. 

Active,  as  curative  measure,  220  ;  active,  for  prophyl- 
axis, 232  ;  classification  of  methods,  218  ;  choice  of 
animals  for,  229  ;  mixed,  220,  234  ;  passive,  as  cura- 


586  INDEX. 

PAGE. 

tlve    measure,    220 ;    passive,    In    prophylaxis,    220 ; 
with   tissue   cells,   1G4  ;   with   toxins,   33. 
Impetisro   contagiosa. 

Staphylococcus   in.   3o4  ;   streptococcus    in.   .".■"iT. 

Incubation   period -'10 

Infection. 

"Air  borne."  3  ;  atrium  of.  3.  35,  30  ;  contact,  b.v,  3  ; 
mixed,  11,  14.  15.  113;  see  individual  diseases; 
"water  borne,"  3  ;  infectious  agents,  classification 
of.   6. 

Infectiousness    and    contagiousness    2 

Infestation      2 

Inflammation. 

Antagonism  of,  to  infections,  4G ;  chemotaxis,  43 ; 
connective  tissue,  inflammatory  rSle  of,  41,  40 ; 
fibrin,  influence  of.  45  ;  injurious  effects  of,  41,  42  ; 
leucocytes  in.  43-45  ;  nature  of,  41  ;  organization  in, 
45 ;  pha^rocytosis  in,  43-45  ;  plasma,  influence  of, 
45 ;  relation  of,  to  virulence  of  bacteria,  42,  43 ; 
role  of,  in  immunity  and  resistance,  41  ;  variations 
in   intensity,  42-44. 

Influenza     10,    .393-399 

Conjunctivitis  in,  37,  397  ;  chronic,  397  ;  contagiousness 
of,  303 ;  epidemics  of.  308 ;  immunity,  308 ;  infec- 
tion atrium.  307  ;  intestinal,  30G ;  intoxication, 
39G  ;  meningitis  in,  300.  307  ;  mixed  and  secondary 
infections  in,  397  ;  otitis  media  in,  39G,  307  ;  peri- 
tonitis in,  306,  307 ;  phagocytosis  in,  396 ;  pneu- 
monia during.  344,  30G ;  prophylaxis,  308 ;  recur- 
rence of,  56.  308  ;  susceptibility.  308  ;  transmission 
of.  307  ;  tuberculosis  during.  307  ;  see  liacilliis  in- 
flcnzw. 

Injuries,  mechanical  and  toxic,  by  bacteria 4 

"Intestinal    group"     of    bacteria 270 

Intoxications,    infectious    15 

Isoagglutinins     104 

Isoprecipitins    121 

Lactoserum    120,    125 

Lamblia     hitefituiaUs     508 

"Leistungskern"    8G,    195 

Lecithin  as  endocomplement    159 

"Leprolin"     450 

Leprosy    10.   445-452 

Animals,  insusceptibility  of.  to.  447 ;  contagiousness 
of.  44G ;  distribution  of  bacilli  in  the  body.  440; 
extension  and  occurrence  of.  445 ;  fish,  relation  of 
to,  448  ;  infection  atria.  448  ;  intercurrent  infections, 
450  ;  phagocytosis  in,  440.  451  ;  potassium  iodid  in 
treatment  of,  450 ;  prophylaxis,  451  ;  protective 
factors  in,  451  ;  serum  therapy  of.  452  ;  spontaneous 
disappearance  of,  450  ;  susceptibility  to,  451  ;  trans- 
mission of.  448  ;  tubercular,  450  ;  see  Bacillus  le/irw. 

Leptothrix,    infections    by    463 

Leptothri.v   hnrcali-t    4G3 

Leptothrix   var/iiialis    4G3 


INDEX.  587 

PAGE. 

Leucocidin    67,    202,    373,   380,   382 

Antitoxin    for,    372 ;    influence    on    phagocytosis,    372. 

Leucocytes. 

Absorption  of  toxins  by,  191  ;  complement  in,  154  ;  for- 
mation of  precipitins  by,  121  ;  immunity,  relation 
to,  176-194  ;  in  inflammations,  43  ;  phagocytic  prop- 
erties of,  43,  44,  45  ;  see  also  individual  diseases ; 
see    Phagocytosis. 

Leucocytic    exudates,    bactericidal    action    of .■;78,    379 

"Loop,"     standard     101 

Leucotoxic    serum     107,     168 

Leucotoxin ;    see   Leucotoxic   Serum. 

"Lumpy   jaw"  ;    see   Actinomycosis. 

Lupus,  influence  of  streptococcus  on 362 

Lymphangitis,     streptococcus    in     354-356 

Lymphatotoxin ;    see    Leucotoxic    Serum. 

Macrocytase    178 

Macroparasites    6 

Macrophages    44,    168,   178,    184 

Madura  foot ;  see  Mycetoma. 

Mai  de  cederas ;   see   Trypanosomiasis   in   animals. 

Malaria     ." 468-483 

/Estivo-autumual,  469  ;  sestivo-autumnal,  parasite  of  ; 
see  Plasmodium  prcecox ;  anemia  in,  474;  "black- 
water  fever"  in,  477 :  cachexia  in,  476 ;  cerebral 
symptoms,  477 ;  epidemiology  of,  477 ;  etiology 
of,  468  ;  fever,  relation  of  to  developmental  cycles 
of  parasites,  474 ;  hemoglobinuric  fever  in,  477  ; 
immunity,  acquired,  481,  482 ;  incubation  period, 
473  ;  intestinal  symptoms.  477  ;  melauemia  in,  474  ; 
methylene  blue  in,  474  ;  mixed  infections,  476 ; 
mosquitoes,  transmission  by,  468 ;  neuralgia  In, 
476 ;  parasites,  localization  of,  477 ;  prophylaxis 
of,  480,  481;  quartan,  469;  quartan,  parasite  of; 
see  Plasmodium  malatiw;  quinin  in  prophylaxis  and 
treatment  of,  470,  477,  481  ;  quotidian,  475  ;  para- 
sites, localization  of,  473,  474,  477 ;  relation  of 
clinical  symptoms  to  developmental  cycles  of  para- 
sites. 473  :  susceptibility  to,  481  ;  tertian,  469 ; 
tertian,  parasite  of;  see  Plasmodium  vivax ;  toxins, 
474.  475 ;  transmission ;  see  Anopheles ;  see  Plas- 
modiurti  of  malaria. 

Malaria  of  birds,   halteridium   in ;   proteosoma   in    483 

Malignant  pustule  ;  see  "Anthrax." 

Mallein 220,  454,  457 

Malta   Fever    333-335 

Accidental  infections.  335 ;  agglutination  reaction  in, 
334 ;  difference  from  typhoid  fever,  334  ;  distribu- 
tion of  bacillus  in  body,  334,  335  ;  immunity,  335  ; 
occurrence,  333  ;  serum,  properties  of,  334 ;  serum 
therapj',  335  ;  transmission,  335  ;  see  Bacillus  meli- 
tensis. 

Measles     559-562 

Complications  and  sequelas.  560 ;  contagiousness  of, 
559  ;  immunity  and  susceptibility.  561  ;  leprosy, 
influence   on,   450 ;    leiicocytes   in.    501  ;   Micrococcus 


•"•^^'^  iXDi:x. 

PAGE. 

vtttanhalis  in,  384;  microorganisms  In,  559; 
propliyluxis,  5G0  ;  racial  Iminunl/.ation,  oOl  ;  resist- 
ance of  virus,  500  ;  recurrences,  501  ;  serum  therapy, 
561  ;    virus,    distribution    of,    559,    560. 

Meat    poisoning. 

Iiaiilhis  botiiliniiK  in.  1250:  liacillus  cntcritidis  in. 
:.:'.>4-'JltS  ;  Bacillus  paratuphosus  in,  285  ;  relation  of 
ptuiiiaiues   to,    i;95. 

Mechanical   and   toxic   injuries 4 

Mediterranean  fever,  see  Malta   fever. 

Meningitis. 

n.  iineitmoiiivc  in.  402;  colon  bacillus  in.  .iOL' :  in  in- 
fluenza. 396 :  micro-organisms  causing,  3S8,  189 ; 
pneumococcus  In,  344,  348,  349 :  secondary,  356, 
357  ;  streptococcus  in,  354,  356,  357  358  ;  tubercu- 
lous,  420. 

Meningitis,  epidemic  cerebrospinal   388-393 

Agglutination  test.  393;  cerebrospiiuil  cliaracter  of, 
■i'M  :  complications,  391  ;  contagiousness  of.  392  ; 
immunity,  acquired,  392  :  lumbar  puncture  for  diag- 
nosis, .''.91  :  metastatic  Infections,  391  :  mixed  and 
secondary  infections  in,  391  :  prophylaxis  of,  392  ; 
secondary  to  rhinitis,  390 ;  serum,  properties  of, 
393  :  susceptibility  to.  392  :  transmission  of,  392 ; 
see  Micrococcus  meuingitidis. 

Meningococcus ;    see    Micrococcus    mcninyifidix. 

Metchnikoff's    theory ;    see    Phagocytosis. 

Methylene  blue,  effect  of,  on  malarial  parasites 474 

Microbic    speciQcity 27 

Micrococcus    cutarrhalis     'AS'.i.    384 

Animals,  susceptibility  of,  to,  384;  bronchitis,  in.  :;.S4, 
391 ;  measles,  in,  384  ;  occurrence  in  i-espirarory 
passages,  383  ;  occurrence  under  normal  conditions, 
384  ;  pneumonia,  in,  337,  344.  384.  392  ;  resemblance 
to  meningococcus,  392 ;  scarlet  fever,  in,  3s4  ; 
whooping-cough,     In,     383. 

Micrococcus  gonorrhccc   (gonococcus^    383 

Antiserum  for,  388  ;  cultivation  of.  384,  385  ;  discovery 
of,  384  ;  endotoxin  of,  385 ;  gonotoxin,  386 ;  Im- 
munization with,  388 ;  infections  with.  384,  388 ; 
morphology,  384 :  phagocytosis  of,  385,  387 ;  re- 
sistance of,  385  ;  toxin,  soluble,  388  ;  see  Gonorrhea. 

Micrococcus  hcmatodes   374 

Micrococcus   mclitensis,  see   liacillus   melitensis. 

Micrococcus     nieuiit(iitidis     (Diplococcus      intruccUularis 

mtiilngitidis,  or  the  meningococcus)    10,  388-393 

Agglutination  of.  393  ;  animals,  susceptibility  of,  390  ; 
antiserum,  properties  of,  392,  393 ;  bronchitis,  in. 
391  ;  conjunctivitis,  in,  391  ;  cultivation.  390  ;  dis- 
covery, 389  ;  endotoxin,  390  ;  excretion  of,  392  ;  im- 
munization with,  39.'{  ;  morphology,  390  ;  pneumonia, 
in,  391  ;  resemblance  to  gonococcus,  389 ;  resem- 
blance to  Micrococcus  cutarrhalis,  392;  resistance, 
390 ;  rhinitis,  in,  391  ;  virulence,  390  ;  see  Mei^in- 
gltls,  epidemic  cerebrospinal. 

Microbic  specificity    27 

Mlcrocj'tase    17S-189 


IVDEX.  589 

PAGE. 

Micro-organisms. 

Early  belief  in,  25 ;  recognition  of,  20 ;  ultrami- 
croscopic,    6. 

Microparasites    6 

Microphages    44,  178,  184,   100 

Microsporon  scpticum    (Klebs) 349 

Milk    bacilli     444 

Mitagylutinin    Ill 

"Monadinin"  of   Klebs 359 

Mucor     467 

Mumps   (epidemic  parotitis ) ■. 56<5 

Mycetoma    462 

Nagana ;   see  Trypanosomiasis   in  animals    493 

Natural    immunity  ;    see    Immunity. 

"Negative  phase"   following  vaccinations 233 

Negri    bodies ;    see    Hydrophobia. 

Nephrotoxin   169,   170 

Neurouophages    179 

Neurotoxin  of  serums    171 

Neurotoxin    of    venom 07,   265 

Oldia     6.     10 

Oidiomycosis     463-467 

In  animals,  467  :  cutaneous,  463  ;  infection  atria, 
465  •  organisms  of.  464 ;  resemblance  to  tubercu- 
losis,   465 ;    systemic,    464 ;    thrush,    466. 

Oidium 464 

Agglutination,    immunization    and    phagocytosis,    467. 

Oidium    alhicans    466 

Oidium  coccidioules   465 

Old  age.   Metchinkoff's  theory  of 168 

Ophthalmia. 

Cytotoxins    in,    173  ;    gonorrheal,    386. 

Opsonic  index   382 

Opsonins   61,   193,  227,  369 

Action  of  salts  on,  194  ;  in  acquired  immunity,  6  ;  see 
Phagocytosis    in    different    diseases. 

Opsonoid    194 

Otitis  media. 

B.  infliienzw  in.  396.  397 :  pneumococcus  in,  348 : 
staphylococcus  in.  377  :  streptococcus  in,  358  :  tuber- 
culous.   420. 

Oxytuberculin     413 

Ozena    402 

Pancreatic  juice,  action  on  toxins 40 

Pancreotoxin     173 

"Paracolon"  bacilli    285 

Parasites,  pathogenic 1,       6 

Parasitism     1 

Parotitis,    epidemic ;    see    Mumps. 
Passive   immunity ;   see   Immunity. 

Paratyphoid   fever    284-288 

Agglutination  reaction  in,  287,  288  ;  blood  cultures  in, 
288  :  characteristics  of  the  disease.  286  ;  endotoxin 
of  bacilli.  287  ;  epidemiology  of,  285  :  as  meat  pois- 
oning, 285  :  occurrence  of  bacilli  in  the  body,  286  : 
properties  of  serum,  287  :  prophylaxis.  287  :  trans- 
mission, 285,  286  :  see  Bacillus  paratijpliosus. 
Passage    58 


r.'.Mi  ixni-:x. 

TAGE. 

rasteur  troiitmeut  :   see  Ilyilruphobia. 

I'athogenesis    4,       5 

roripneiimonia  of  cattle 11,     12 

Periostitis    albuminosa    377 

Periostitis,   staphylococcus   in 377 

Peritonitis. 

Colon    liacillus    in.    SO."} :    b.v    influenza    bacillus.    300. 
307  :     pneuniocoocus    in.    34S.    340  :    staphylococcus 
in.  377:  streptococcus  in,  354.  357;  tuberculous,  420. 
Pertussis ;     see    Whooping-cough. 

Pfeiffer's    phenomenon 06,    131,  132 

In  identifying  the  vibrio  of  cholera,  305  ;  role  of  leu- 
cocytes  in,    ISS. 
Phagocytic    (Metchnikoff's)    theory  of  immunity ....  17('>.    104 
Comparison    of.    with    the    side-chain    theory    of    Ehr- 
lich.    212,    215:   see   Phagocytosis. 

Phagocytosis    31,    44,    176-194,    215 

In  active  immunity.  50,  00,  102.  103  :  chemotaxis  in, 
177.  185:  fixators,  influence  of,  100:  in  inflamma- 
tions. 43  :  intestinal,  41.  177  :  intravascular,  188  ; 
leucocidin,  influence  of,  372  ;  in  nutrition.  172  :  op- 
sonins., role  of.  103  :  in  passive  inimunitj-,  60,  102, 
103  :  relation  of  to  virulence  of  bacteria,  184,  187  ; 
in  resorption,  178 :  serum,  influence  of.  187.  193 ; 
in  vitro.  40.  103  :  see  under  the  individual  micro- 
organisms  and   diseases ;    see    Opsonins. 

Phagolysis    181,  182,   188.  190 

Phallin     264 

Phrynolysin     268 

Phytoprecipitins     120 

Plaoiomonas  urinaria   508 

Plague     lU,    315-327 

Agglutination  reaction.  320.  327  :  animals,  suscepti- 
bility of.  310  :  conthgiousness,  322  :  diagnosis,  bac- 
teriologic.  323  :  dissemination  of  bacillus  by  urine, 
feces,  sputum.  322  ;  epidemiology.  320.  323  :  foci  of, 
320 :  immunity,  56,  60,  324,  325 :  infection  atria, 
322 :  mixed  immunization  in,  234.  324  :  mixed  in- 
fection in.  323  :  occurrence,  315 :  houses.  321  : 
prophylaxis.  323  :  in  rats,  320  :  serum  therapy.  325, 
32(". :  transmission  by  fleas.  320,  321  :  transmission 
from  rat  to  man.  320,  321  :  vaccination,  58,  218, 
323  :   vaccines.  323,  324  :  see  Bacillus  pestis. 

Plasmin    of    Buchner 68,  219 

Plasmodia    of    malaria 4,    10,    468 

Anopheles  mosquito  as  host  of,  9,  469  ;  asexual  cycle. 
469 :  development  in  anopheles.  470 :  development 
in  man.  469 :  discovery  of.  468 :  flagella  of.  468 : 
macrogamete.  470  :  merozoites.  470  :  methylene  blue, 
effect  of.  474  :  microgaraete,  471 ;  microgametocyte, 
470  i  oocyst,  471  :  ookinet,  471  :  schizogony,  470  ; 
sexual  cycle.  470  :  species  of.  400  :  spermatozoites. 
408:  sporocyte.  470:  sporogony.  471:  spnrozoites. 
471 ;    see    Malaria. 

Plasmodium    vialariw    ■  469 

Relation  to  clinical  symptoms,  473:  sexual   and  asex- 
ual   cycles   of,    472 :    virulence,    474. 
PlasniofUt'm    prcecox    469 


INDEX.  591 

PAGE. 

Relation  to  clinical  syniptoms,  47:i  ;  sexual  and  asexual 
cycles   of,    472 ;    virulence,    473. 

Plasmodium    vivax    4G9 

Asexual    cycle    of,    4G0,    470 ;    relation    of    to    clinical 
symptoms,  473  ;  sexual  cycle  of,  470,  471  ;  virulence  474 
Pneumococcus  ;   see  Diplococmis  pneiimonUe. 

Pneumonia   330-348 

Agglutination  reaction,  347 ;  B.  pneumoniai  in,  402 
bacteria  causing,  336,  337 ;  causes,  predisposing, 
343  ;  complications,  343,  344,  348  ;  contagiousness, 
342  :  immunity  and  susceptibility,  .56,  34.5  ;  infection 
atrium  and  method  of  infection,  340  :  influenza  bacil- 
lus in,  396  ;  leucocytes,  345  ;  metastatic  infections, 
348  ;  phagocytosis,  345 ;  meningococcus  in,  301  ; 
Micrococcus  catarrhalis  in,  384,  392  ;  mixed  infec- 
tions in,  344 ;  polyvalent  serum  for.  347  ;  prophy- 
laxis, 344  ;  recurrences,  345  ;  Roemer's  serum,  347  ; 
serum  properties,  345 ;  serum  therapy,  346.  347 ; 
staphylococcus  in,  377  ;  streptococcus  in,  354,  355, 
356  :  vaccination,  345  ;  see  Diplococcus  pneumonicB 
and  other  bacteria  enumerated  on  page  336. 

Pneumotoxln     339 

Pollantin    263 

Pollens. 

As  cause  of  hay  fever,  262  ;  antitoxin  for,  263. 

Polyceptors 155 

Polyvalent   serums. 

For  pneumococcus,  347  ;  for  staphylococcus,  383  ; 
for   streptococcus,    232,    306. 

"Positive   phase"    following  vaccination 233 

Postmortem    invasion    302 

Precipitate    120,   124,   125 

Precipitation   reaction    106,   119 

Agglutination,  relation  to,  117 ;  as  clinical  reaction, 
119  :  with  colloids  and  electrolytes,  128,  129  ; 
forensic  use  of,  63,  125  :  precipitation,  group  reac- 
tion. 125,  126  :  meats,  differentiation  of,  127  ;  physi- 
cal chemistry  in  the  study  of,  129  ;  specific  inhibi- 
tion. 122  ;  technic,  126  ;  use  of  in  studying  reactions 
of    immunity,    206. 

Precipitins    119-129 

Antiprecipitins,  123  :  autoprecipitins  121  :  bacterial, 
63,  119,  233,  314  ;  formation  of,  121  :  isoprecipitins, 
121  :  lactoserum,  120 :  phytoprecipitlns,  120  :  re- 
sistance to  ferments,  heat,  etc.,  122  :  serum  precipi- 
tins, immune,  63  :  serum  precipitins,  normal,  55 ; 
structure   of,    122 ;   zooprecipitins,    120. 

Precipitogens    120 

Precipitoids     12§ 

Pregnancy,   serum   diagnosis 172 

Preparator     148 

Proagglutinoids    109 

Prophylactic  injections,  classification  of  methods 218 

Protective    inoculation ;    see    Vaccination. 

Proteins     220 

Proteosoma  in  malaria  of  birds 483 

Prototoxin    83,  20v> 

Protoxoids    82,  209 


o!>2  IXDKX. 

PAGE. 

Protozoa,  infoctlons  with 408,   509 

rseudodiphihiTia  baoilli    243,  244,   425 

I'seiuioinlliH'iiza  bacilli    394 

rseudotuberculosis   of  animals 444 

Ptomalns   in  meat 205 

Pyocyanase     61,  260 

Pyocyanin     260 

Pyocyanolysin     2G0 

Ptiroplasma    hovis :    see    Texas    fever. 
Pi/rophif^iitn   ho7tiiiiis:   sec   Spotted   fever 
Pyroplasmosis :    see    Spotted    fever    and    Texas    fever. 
Rabies ;    see    Hydrophobia. 

Hadium,  effect  on  venom    207 

Rats  .in  epidemics* of  plague   320,  321 

Rattlesnake  venom. 

Antiserum   for,   207 ;   immunization   with.   210. 

Ray   fungus ;    see*  Actinomyces 320,    321 

Receptors. 

Bacterial.  152:  function  of.  52.  f<~.  RS  :  immunify.  re- 
lation to.  100;  loss  of.  as  cause  of  immunity,  240; 
multiplicity  of.  SO.  208;  new  formation  of,  100,  205, 
207;  nutrition,  relation  to.  105:  of  first  order,  89, 
200.  207;  of  second  order,  114  203.  207.  209;  of 
the  third  order,  150.  203,  207 :  synonym  for  side 
chain.  107  ;  tetanophile  receptors  of  nervous  tissue, 
252  :  types  of.  207  ;  see  different  antibodies. 

Kelapsinir  fever    10,   40.3-406 

Agerlutination  test,  406  ;  immunity  and  susceptibility, 
404,  400;  organism  of;  see  Rpirocheta  nhcr- 
mrieri :  phagocytosis  in.  405  ;  propliylaxis,  404  ; 
serum  properties.  405.  400 ;  serum  tlierapy,  400 ; 
transmission  of  by  bedbugs,  404. 
Resistance,  natural  ;  see  Immunity,  natural. 
Resorption. 

Of   foreign   cells,   179 ;   of  native   cells,   178. 

Rheumatic  fever   359,  360 

"Agonal  invasions  in,  359  :  antistreptococcus  serum  in, 
308 ;  bacillus  of  Achalme  in.  359 :  diplococcus 
Cstrentococcus)  in.  300 ;  experimental.  359.  360 ; 
micro-organisms  found  in  lesions,  350  ;  staphylococ- 
cus in,  359 ;  streptococcus  in,  354,  359.  360 ; 
/.innctosis  transTiicens,  359. 
Rhinitis. 

Meningococcus  in.  301  ;  pneumococcus  in,  348 ;  pri- 
mary to  meningitis.  390;  staphylococcus  in,  377; 
Ixhiiiitis   fiJ}ri)>osa,    237. 

Rhinoscleroma    402 

Ricin    0,  264 

Antiricin,  63  ;  Ehrlich's  use  of  in  studying  nature  of 
antitoxic  action,  201,  202;  hemagglutinin  in,  104. 

Robin     264 

R()theln.  see  German  measles. 

SnccJiaromi/cosis   homiiih 464 

Salamjvnder   poison,   antitoxin   for 90 

Saprophytes    1 

In    tetanus    248 

Sarcnrjistis    liominifi:    see    Sarcosporidia. 


INDEX.  r/J3 

PAGE. 

Sarcosporidia. 

Morphology,  occurrence  and  proliferation,  r»04,  ijO.") ; 
SarcocysMs    liommis,    505. 

Scarlatina ;    see   Scarlet   fever. 

Scarlet   fever    (scarlatina) 55G-559 

Agglutination  of  streptococci  by  serum,  369,  370  ;  con- 
tagiousness, 557  ;  Cyclastcr  scarlatinalis  in,  55G ; 
Diplococcus  scarlatinoe,  11  ;  leucocytes  in,  558 ; 
Micrococcus  catarrhalis,  384 ;  micro-organisms  in, 
557 ;  prophylaxis,  557 ;  protozoa  in,  10,  556 ; 
resistance  of  virus,  557  ;  serum  therapy,  558,  559  ; 
streptococcus  in.  14,  15,  186,  354,  355,  358,  361, 
556;  Streptococcus  scarlatina;,  361;  immunity  and 
susceptibility,  56,  558;  serum  therapy  (antistrep- 
tococcus),  366,   368,   558;   transmission,   557. 

Scorpion,  toxin  and  antitoxin 90,  268 

Sensitization     145 

Serpent  ulcer. 

Pneumococcus  in,  348,  349  ;  treatment  with  antipneu- 
mococcus    serum     (lloemer),    349. 

Serums,   purity    of 76,  221 

Serum  therapy,  principles  of   218-234 

Antitoxins,  221,  226 ;  bactericidal  serums,  226,  232 ; 
classification  of  methods,  218 ;  curative  injections, 
220,  223,  227 ;  prophylactic  injections.  218,  226, 
227  ;    see   also   under   the   different  diseases. 

Sheep-pox ;   see  Clavelde. 

Side-chain  theory  of  Ehrlich    195-217 

Amboceptor  formation,  150 ;  agglutinin  formation, 
114 ;  antitoxin  formation,  86,  89 ;  applied  to  cell 
nutrition,  195  ;  as  applied  to  immunity,  199  ;  chem- 
ical processes,  78,  200,  205,  208  ;  complements,  153, 
210 ;  essential  tenets  of,  200 ;  haptophores,  197 ; 
"Leistunf/skern/'  195  ;  Metclinikoff's  phagocytic  the- 
ory, comparison  with,  212.  217 ;  precipitin  forma- 
tion, 121  ;  receptor  proliferation,  205 ;  receptors, 
types   of,   207 ;   side   chains,    195. 

Sleeping  sickness    486-490 

Anatomic  lesions  of,  489 ;  bacteria  in,  487 ;  occur- 
rence. 486.  487  ;  symptoms  of,  488,  489  ;  transmis- 
sion of,  488  ;  Trypanosomatic  fever,  relation  to,  489, 
490 ;    ti'ypanosomes    in,    487 ;    see    Trypanosomiasis. 

Smallpox     541-555 

Bacteria  in.  542,  548  ;  conversion,  into  vaccinia,  541, 
542 ;  cyclic  nature  of  symptoms,  547 ;  Cytoryctes 
variolw  s.  vacciniw,  548 ;  dissemination  of  virus, 
546 ;  etiology.  542  ;  fetal,  548  ;  immunity  and  sus- 
ceptibility, 56,  554  ;  incubation  period,  547  ;  infec- 
tion atrium,  546 ;  inoculation  into  calves,  541  ; 
Jennerization,  549  ;  leucocytes  in,  554  ;  mixed  (sec- 
ondary) infections,  15,  548  ;  nonfiltrability  of  virus, 
542 ;  prophylaxis,  548 ;  protozoon-llke  bodies  in, 
11,  542 ;  relation  to  vaccinia.  57,  541  ;  revaccina- 
tion,  552,  553 ;  serum  properties,  554 ;  transmis- 
sion, 546 :  vaccination,  548 ;  vaccine,  contamina- 
tions of,  551,  552  ;  vaccine,  durability  of,  551  ;  .viru- 
lence, variations  in,  547  ;  virus,  distribution  in  the 
body,    547.  ; 


594  IXDEX. 

PAGE. 

Smallpox  and  vaccinia 541,  5")") 

Smegma    bacilli    443 

Snako  bitos    264,  2G8 

Soft    chancre    or    chancroid     8!)9-401 

In  animals,  400:  bacillus  of.  400;  Immunity,  401  ;  in- 
dependence, .300  ;  infectiousness  of,  309  ;  phago- 
cytosis,   400,    401. 

Specific  infections    9 

Spcrmnphiliis     columhiaiuts     as     host     of     Pyroplasma 

hominis    .    498 

Spermotoxin    '.' .       165,  160 

Spider  poison,   antitoxin   foi- 90 

Spirochrta  nhcnn cirri 10,  403 

Agghuinins  for,  400  :  animals,  susceptiblllly  of.  404  ; 
antiserums,  properties  of.  405 ;  distribution  in  the 
body,  403  ;  morphology,  403  ;  occurrence  in  bedbugs, 
404  :   phagocytosis  of,  405  ;   see  Kelapsing  fever. 

SpirocJieta   rinUida    (see  syphilis) 525,   526 

"Spotted    fever"    '. 497,  498 

Piiroplaaiiia    hominis   in 497 

StaphiilocnccK.i  pyoqcnea.  or  staphylococcus 370-383 

Agglutination,  02.  3S2  :  amyloid  degeneration.  375 ; 
animals,  susceptibility  of.  375,  376 ;  antiserums, 
properties.  3S0  :  bactericidal  action  of  leucocytic 
exudates.  378.  370  :  bacterlolysln.  379.  380 ;  dis- 
covery. 350 :  endotoxin,  373 ;  ferments  of,  371  ; 
hemolytic  action,  5.  371.  372:  Immunity,  186.  379, 
380 ;  leucocidin.  372.  373.  380.  382 ;  leucocytes 
in  infections.  378.  379  :  leucotactic  substance.  375  : 
mixed  infections.  378 :  morphology,  370 ;  necrotiz- 
ing substance,  375 :  pathogenic  powers.  37.  336. 
344,  354,  359.  376,  378.  389  ;  opsonins  in  phagocv- 
tosls  of,  382 ;  phagocytosis,  378.  370,  380,  382 : 
pigment  formation.  374  :  polyvalent  serum.  383 : 
resistance.  374.  375  ;  staphylolysin,  271.  372,  373, 
375.  380  :  symbiosis  with  Amelia  coli,  502  :  symbio- 
sis with  7?.  influenza;,  394  :  toxicity  of  culture 
filtrates,  372,  373  :  toxin,  soluble,  375  ;  vaccination 
against,  381  ;  varieties.  373.  374 ;  virulence,  37G. 
Staphylolysin  ;    see    Staphylococcus. 

S<tcgomr/ia  fasciata  and  its  relation  to  yellow  fever 531 

Streptococci   in   scarlet   fever 14,   354,   355,    358,   361 

Streptococcus   brevis 350 

Streptococcus    erysipelatis    350 

Streptococcus    longus    350 

Streptococcus  mucosus  capsulaius    351 

Streptococcus    pyogenes 349-370 

Agglutination,  92,  369,  370  ;  animals,  susceptibility  of. 
352  ;  antagonism  for  B.  anthracis,  329,  362  ;  for  B. 
tuberculosis.  350 :  antlstreptococcus  serum,  proper- 
ties of,  362.  368  :  antistreptocolysin,  353  ;  bacterio- 
tropic  substances,  369 :  Coley's  mixture,  362 ;  cul- 
tivation, 351  ;  in  diphtheria,  238,  358 ;  discovery, 
350 :  endotoxin.  353  :  erysipelas.  350,  354,  355 : 
immunity,  186.  363,  364,  365:  Infection  atria.  358; 
infections,  miscellaneous,  354,  362 :  in  Influenza, 
397 ;  leucocytes  and  leucocytosls,  363.  364 :  lupus. 
Influence  on,  262 ;  In  meningitis.  354,  389 ;  in 
milk,   357 ;    morphology,    350 ;    opsonins,    369 ;    yha- 


INDEX.  rj95 

X'AGE. 

gocytosis,  3G3,  364 ;  in  pneumonia,  330.  344,  354, 
355,  356 ;  resemljlance  to  pneumococcus,  338 ;  re- 
sistance, 351,  352;  in  rheumatic  fever,  354,  359; 
in  scarlet  fever,  14,  354,  355,  358,  366;  serum  llier- 
apy,  367-360 ;  serums,  univalent  and  polyvalent, 
365 ;  streptocolysin,  353,  354 ;  symbiosis  with 
B.  influenza;,  394  ;  tissue  reactions,  42  ;  toxic  prop- 
erties, 353.  354,  362 ;  toxin  for  erythrocytes ;  see 
Streptocolysin  ;  toxin  for  leucocytes.  354  ;  in  tuber- 
culosis, 355,  356,  424,  425 ;  tumors,  inilucnce  on, 
362  ;  in  typhoid  fever,  275  ;  unity,  question  of,  365  ; 
varieties,    350 ;    virulence,    352. 

Streptococcus    scarlatinal     361 

Streptocolysin 353,    354 

Streptothrix,     Infections     w^ith     463 

Streptothrix    inadurw     462 

Substance  sensiMUsatricc    148,   217 

Summer    diarrheas ;    see    Dysentery,    acute   epidemic. 

Surra ;    see    Trypanosomiasis    in    animals 494 

Susceptibility     18,     53,     54 

See   the   individual    diseases. 
Symptomatic    anthrax. 

Antitoxin,    90 ;    vaccination    against,    219. 

Syncytiolysin     171 

Synonyms    217 

Syntoxoids     83,    209 

Syphilis     10,    522-529 

Animals,  non-susceptibility  of,  522 ;  bacillus  of  De 
Lisle  and  Julien,  522  ;  bacillus  of  Joseph  and  Plor- 
kowski,  522 ;  bacillus  of  Lustgarten,  522 ;  CoUe's 
law,  528 ;  immunity  and  susceptibility,  54,  527 ; 
inheritance,  527 ;  micro-organisms  found  in,  522 ; 
monkeys,  transmission  to,  12,  522 ;  reinfection, 
527 ;  SpirocJieta  pallida  in,  525 ;  transmission, 
526 ;  virulence,  variations  in,  527  ;  virus,  distribu- 
tion of,   526 ;  virus,   non-fllterability  of,   526. 

Tetanolysin     -. 249,     250 

Antitetanolysin,  223  ;  neutralization  by  cholesterin,  91. 

Tetanospasmin    249,    250 

Tetanus    10,    244-256 

Agglutination  reaction,  256 ;  animals,  susceptibility 
of,  51  ;  cerebral,  251 ;  dirt  and  necrotic  tissue,  In- 
fluence of,  247 ;  dolorosa,  251  ;  excretion  of  toxin, 
250 ;  Fourth  of  July,  248,  252 ;  "head  tetanus," 
251  ;  in  horses,  252 ;  immunitv  and  susceptibility, 
18,  60,  185,  249,  251 ;  "idiopathic,"  248  ;  incuba- 
tion period,  249  ;  leucocytes,  in  absorption  of  toxin, 
250  ;  local,  251 ;  lumbar  puncture,  255  ;  mixed  infec- 
tions, 14,  248,  249  ;  nervous  tissue,  in  fixation  and 
transport  of  toxin,  250  ;  non-contagiousness  of,  3  ; 
occurrence  of  bacillus  in  the  body,  249  ;  occurrence 
of  toxin  in  the  body,  250  ;  pathogenesis,  250,  251 ; 
phagocytosis  in,  185,  248  ;  puerperal,  252  ;  rheumat- 
icus,  248 ;  seasons  in  relation  to  prevalence,  248 ; 
serum  therapy  and  prophylaxis,  224,  253-255 ; 
toxin  (see  B.  tetania  toxin  of)  ;  treatment  of 
wounds,  252 ;  Wassermann's  experiment,  250 ; 
wounds  favoring  development  of,  247  ;  see  Bacillus 
tetani. 


59G  r\Df:x. 

PAGE. 

Texas    fever    -ii^'^ 

Thrush     •l*j*> 

Organisms  of,  40(3 ;  susceptibility  to,  407  ;  systemic 
infections,   466. 

Thyrotoxin     1"3 

"Tick    fever"  ;    see   "Spotted   fever." 

Timothy    bacillus     444 

Toxins. 

Animal.  0.  204-2G8 ;  attenuation  of,  70 ;  l>ac- 
terial,  0.  2:i5 ;  see  individual  bacteria ;  cliem- 
otaxls,  influence  on,  ISo,  354,  372 ;  crotln, 
204 ;  degenerative  changes  in,  80,  209 ;  dis- 
covery of.  33 ;  effects  of,  4,  5 ;  endotoxins,  6. 
20,  OS ;  see  individual  bacteria ;  gastric  juice,  de- 
structive action,  30 ;  haptophores  of,  70,  209 ;  see 
side-chain  theory  ;  immunization  with,  00.  70,  220 ; 
incubation  period  of,  C5,  251  ;  intracellular ;  see 
Endotoxins ;  leucocidin.  372 :  leucocytes  in  absorp- 
tion of.  45,  101  ;  modifications  by  age,  85 ;  neu- 
tralization by  antitoxins,  48.  78,  200 ;  pancreatic 
juice,  destructive  action,  40;  phallin,  204;  of 
pollens.  202  ;  precipitation  of,  06  ;  preparation.  t>0  ; 
properties  of,  05,  208  ;  as  receptors  of,  second  order, 
207 ;  ricin.  204 ;  robin.  204 ;  secondary  or  adven- 
titious, 07  ;  selective  action  of,  5  ;  toxin  spectrum, 
81,  200  ;  standardization  of,  72  ;  staphylolysin,  371  ; 
structure.  78  ;  toxophores,  80,  200 ;  see  side-chain 
theory ;  union  with  tissue  cells.  66,  87,  200,  204. 
224,  222,  252 ;  vegetable,  6,  262-264 ;  see  individ- 
ual   micro-organisms. 

Toxoids    80-83,    209 

Toxon 82,    209,    242 

Toxophorous  group,    toxophore    80,    207 

Trichomonas  iiitestinalis,  morphologv   and   pathogenicity 

of    507,    508 

Tricfwmonas    vaginalis     507 

Trichoijhvton     467 

Tritotoxin      83,     209 

Trypanosoma    483 

Agglutination     of,     485 ;     cultivation     of,     492,     404 ; 
■     morphology  of,   484  ;  multiplication   of,   485  ;   rosotte 
formation    by,    485 ;   sleeping   sickness.    487 ;    species 
of.    484,   485.   490 ;    trypanosomatic   fever,    480. 

Trypanosomatic    fever     485,    486 

Sleeping  slclcness.  relation  to.  480,  400 ;  symptoms 
of,    480 :    trypanosomes    in,   486. 

Trypanosomiasis    483-497 

Agglutination  reactions,  497:  immunity  and  suscep- 
tibility, 405;  in  man.  485-400;  parasites,  occurrence 
of  in  the  blood,  491  ;  serum  therapy  of.  406 ; 
'trypanroth"  in  treatment  of.  490 ;  vaccination 
in,"  496 ;  see  Sleeping  sickness  and  Trypanosomatic 
fever. 

Trypanosomiasis   in    animals    490-495 

bourine,  495 ;  horses,  cattle  and  mules,  493-405 ; 
mat  de  rederas,  405 ;  nagana,  403 ;  in  rats,  491  ; 
surra,    404  ;    symptomatology,    491. 


INDEX.  597 

PAGE. 

"Trypanroth"    In    treatment    of    trypanosomiasis    490 

Tsetse    flies,    in    transmission    of    trypanosomiasis ;    see 
Trypanosomiasis. 

Tuberculin  of  Kocli  and  others 219,   220,  412,   413,   414 

Dangers,  errors  and  limitations  in  use,  434,  435 ; 
diagnostic  use  of,  432-436,  442  ;  disturbances  caused 
by,  433;  Immunization  with,  411,  431,  432;  prepara- 
tion of,  412  ;  principles  of  action,  437  ;  _speclficlty 
of.  434,  435  ;  standardization  of,  412,  414  ;  therapy, 
436,    437. 

Tuberculocidin    413 

Tuberculosis     10,    407-443 

Agglutination  as  an  index  of  immunity  to, 
437 ;  agglutination  reaction,  438,  440 ;  amy- 
loid degeneration  in,  424 ;  "anatomic  tubercle," 
419  ;  m  animals,  427,  441 ;  avian,  442  ;  bovine,  441 ; 
bovine,  relation  of,  to  human,  415-417 ;  congenital, 
417  ;  disinfection  in,  426  :  dissemination  by  means 
of  phagocytes,  421  ;  "droplet  infection,"  418 ; 
"dust  infection,"  418 ;  healing,  spontaneous,  420 ; 
heredity  in,  429 ;  immunity  and  susceptibility,  18, 
19.  61,  427,  430-432,  437 ;  Immunization,  mixed, 
439 ;  Infection  atria,  418,  420 ;  infectiveness  of, 
407  ;  latent.  418  ;  lupus  vulgaris,  419  ;  metastases 
in,  420 ;  miliary,  421 ;  mixed  infections  in,  424 ; 
organs  attacked,  419-421 ;  phagocytosis,  421,  422 ; 
pneumonia  during,  344 ;  predisposing  factors  to, 
42S,  429 ;  primary  and  secondary,  421  ;  prophy- 
laxis. 425,  427 ;  pulmonary.  418 :  serum  therapy, 
425,  438  :  streptococcus  in,  355,  350  ;  tissue  changes 
in,  5.  422-425 ;  tuberculin  in  diagnosis.  432-430 ; 
ulcerative,    419 ;    vaccination    against,    439. 

Tumors,    influence   of   streptococcus    on    302 

Turtle    poison,    antitoxin   for    90 

Typhoid   fever    10,    209-284 

Agglutination  reaction,  7,  95.  283,  284 ;  antibodies, 
origin  of,  190  ;  bacillemia.  272,  273  ;  bacilli,  distri- 
bution in  the  body,  273,  274  ;  blood  cultures  for  di- 
agnosis. 273.  284 ;  "dust"  infection,  272 ;  epidemi- 
ology of,  271  ;  flies  as  carriers,  272  ;  immunity  and 
susceptibility,  56,  60,  61.  275 ;  infection  atrium, 
272 ;  leucocytes,  274.  277 ;  leucotoxin  in  experi- 
mental infections,  168 ;  mixed  immunization,  234, 
282  ;  mixed  infections  in,  275  ;  serum  properties,  20 
prophylaxis.  278 ;  serum  prophylaxis,  279 ;  serum 
therapy,  230,  282 :  therapy,  active  immunization, 
283 ;  therapy  of  Jez.  283 ;  vaccines  and  vaccina- 
tion,  58,   218,   279,   282  ;   see  B.   typhosus. 

Typhus    fever    10,    538-541 

Conditions  for  development,  538  ;  contagiousness,  539  ; 
fomites,  539  ;  micro-organisms  in,  538 ;  occurrence, 
538 ;  prophylaxis,  539 ;  pyroplasma  ( ?)  in,  538  ; 
serum    therapy,    539 ;    transmission,    539. 

Ultramicroscopic   micro-organisms    12 

Uncinaria   duodenalis    4 

Undulant  fever ;    see  Malta  fever. 

Univalent    serums     366 

Urease     ' .  '     90 


598  IXDKX. 

PAGE. 

Vaccination    I'S,   57.   21S-220,  232-234 

Antibodies  proiiiicetl  by,  23;?  ;  duration  of  resistance 
caused  by,  2.'{2 ;  incubation  period,  relation  to, 
234;  see  Smallpox  and  Hydrophobia;  opsonins,  in-. 
crease  of,  234 ;  •■positive''  and  "negative  phases," 
233 :  substances  used  for,  21S-22U ;  see  the  indi- 
vidual  diseases. 

Vaccines    218-220,    232-234 

See   the   Individual   diseases. 
Vaccinia ;    see    Smallpox   and   Vaccinia. 
Varicella;    see    Chlckenpox. 

Variola    inoculata    o4G,    591 

Variola ;    see    Smallpox. 

Venoms   24,  G6,  78,  S5,  15S-1G0,  2G4-2G8 

Amboceptors  and  complements,  150,  266 ;  antiveiiins, 
63.  267,  268 ;  character  of,  from  different  snaljes, 
2(!5 ;  cobra-Iecithid,  160,  266 ;  cytotoxins  of,  265 ; 
endocomplements  for,  159,  266;  endotheliotoxin  of, 
265  ;  ferments  of,  266  ;  hemagglutinins  of,  158,  265  ; 
hemolysin  of.  158,  265 :  hemorrhapin,  159.  265 ; 
incubation  period,  66,  267;  lecithin  as  comple- 
ment, 159,  266 ;  neurotoxin  of,  158,  265 ;  radium, 
effect  of,  267  ;  structure  of  cytotoxins  of,  266  ;  tox- 
ins of,  158 ;  toxoids  of,  265. 
Vibrio  cholera:. 

Acquired  immunity  to,  186;  action  of  gastric  juice  on, 
39  ;  active'  immunity,  formation  of  specific  precipi- 
tin in,  314  ;  agglutination  of,  by  normal  serum,  02  ; 
agglutination  of,  315;  agglutinins,  314;  attenua- 
tion of,  57 ;  autolytic  products,  vaccination  with, 
:U3  ;  discovery,  304  ;  endotoxin  of,  309  ;  identifica- 
tion of,  by  agglutination  reaction  and  by  Pfeiffer 
experiment.  305  ;  in  Pfeiffer's  phenomenon,  131  ; 
in  stools  of  convalescents,  307  ;  location  in  infected 
body,  310 ;  morphology,  staining  properties  and 
cultivation  of,  304,  305  ;  non-neutralization  of  endo- 
toxin of,  by  its  specific  bactericidal  serum,  137  ;  oc- 
currence of  water,  307  ;  resistance  and  viability  of, 
306  ;  see  Cholera  ;  symbiosis  with  Ameha  coll,  502  ; 
soluble  toxin  (  ?)  310  ;  specificity  of.  9  ;  toxicity  of 
culture  filtrates,  309  ;  toxicity  of  killed  cultures,  309. 

Vihrio    metchnikovi 33 

Virulence. 

Increase  of,  in  the  presence  of  other  micro-organisms, 
14  ;  influence  of,  on  inflammatory  reaction,  42  ;  rela- 
tion of,  to  phagocytosis,  184 ;  see  different  micro- 
organisms. 

Wasp    poison,    antitoxin    for     90 

Whooping  cough    (pertussis)    562-566 

Contagiousness,  564,  565  ;  cultural  characteristics  and 
lithogenicity  of  the  influenza-like  bacillus,  562 
563 ;  immunity  and  susceptibility,  505 :  influeuza- 
like  bacillus  in,  562 ;  influenza-like  bacillus,  rela- 
tion to  whooping  cough,  564 ;  Micrococcus  catar- 
rhnlis  in,  383 ;  micro-organisms  in,  562 ;  prophyl- 
axis, 565 ;  pseudo-influenza  bacilli  in,  395 ;  serum 
therapy,    505  ;    virus,    dissemination    of,    564. 


MDEX.  599 

„,i'    i        1  >!  ■  -.        .  PAGE. 

Water-borne       eiademics ;    cholera,    dysentery,    typhoid. 

071       OflO      '>i\Si 

Welch,  hypothesis  of '  "     '  r/^ 

Widal   reaction    '.'.'.'.'.'.'.'.'. 02'    111 

See    Agglutination.  "' 

Wool-sorters'  disease;   see  An(hra.\-. 
Wright's    method    of    vaccination. 

Staphylococcus    infections,    381  ;    typhoid    fever,    279, 

Yellow   fever    Kj     goo-SSS 

Acclimatization,  question  of,  537  ;  altitude  and  mois- 
ture, relation  to,  583 ;  Bacillva  icteroidcs  in.  530 
531  ;  cold,  relation  to,  533 ;  epidemiology,  533  ;  fo- 
mites,  532,  533 :  immunity  acquired,  332,  538  • 
importation  by  ships,  530 ;  incubation  period,  532  • 
mosquito  theory  of,  530;  see  also  Steriomyia  fasci- 
ata;  non-contagiousness  of,  533;  occurrence,  529- 
prophylaxis  and  quarantine  of.  533,  534.  536  537  ' 
virus,  filterability  of,  532 ;  virus,  resistance  of,' 
536 ;    serum  therapy,   538  ;   susceptibility  to,   537. 

Zone,    contagious    _ 2     3 

Zo(5precipitins     ' 120 

Zootoxins     '      268 

Zwischenl-ih-per,   synonyms  for 14.8 

Zymotoxic  groups 108 


000  i\in:\. 

CORRECTIONS. 


I'a^c  S,  14th  line  fioiii  hoitdin:  iiistoad  of  "Strong,"  rend 
"Miisjirave  and  ClogK." 

I'ago  12,  4th  line  from  top:  instead  of  "Unstained  ability," 
read   "Unstainability." 

I'age  27  :  between  the  12th  and  i;Uh  lines  from  top  a  line 
is  omitted.  It  should  read  :  "Other  students,  especially 
I'asteur  and  Koch,  soon  took  up  the  study  of  anthrax."  etc.  ; 
the  i;Uh  line  is  repeated. 

l*ai,'e  57,  14th  line  from  bottom  :  instead  of  "s-arloloid," 
read   "variolata  Inoculala.  ' 

Page  Gl,  4tli  line  from  top :  instead  of  "poisons,"  read 
"opsonins." 

Page  So,  18th  line  from  bottom :  instead  of  "Part  II, 
Chapter  III,"   read  "pages  158-100." 

Page  85,  4th  line  from  bottom  :  instead  of  "equaled,"  read 
"equalled." 

Page  107,  i;>th  line  from  bottom:  instead  of  "flagellffi" 
read  "flagoUa." 

I'age  158,  footnote  :  instead  of  "Chapter  III,"  read  "page 
204." 

Page  181,  3rd  line  from  bottom  :  instead  of  "phenomena" 
read    "phenomenon." 

Page  200.  4th  line  from  top  :  instead  of  "crawfish,"  read 
"spider-crab." 

Page  217  :  instead  of  "opsinogenous."  read  "opsonigenous." 

Page  231,  9th  line^  from  bottom  :  instead  of  "simulating." 
read  "stimulating." 

Page  204  :  The  description  of  the  poison  fangs  of  snalies 
applies  to  the  chief  poisonous  snakes  of  North  America, 
which  are  "pit  vipers"  ;  another  class  of  poisonous  snakes, 
among  wliich  are  included  the  cobra,  and  the  coral  snake  of 
North   America,    possess   immovable  poison   fangs. 

Page  413,  3rd  line  from  bottom  :  instead  of  "toxins  of 
tuberculins,"     read     "toxins    or     tuberculins." 

Page  485.  5th  line  from  bottom  :  instead  of  "Nepreu," 
read  "Nepveu." 

I'age  485,  2d  line  from  bottom,  and  page  490,  8th  line 
from  bottom  :  Instead  of  "T.  ncprevi"  read  "T.  nepveui." 

Page  511.  14th  line  from  bottom:  instead  of  "microscopic," 
read    "ultramicroscopic." 


^j^^ 


//o'^  />i>^^^^  :v-,  ^  ^-^y.^;:^^^^  z4^. 


